Ok, I'll chime in... My couch in my formal LR has two cushions. I also have a few pillows on the couch. I've had to arrange my pillows now so that the "open" space is entirely on one side. Otherwise, my DH always sits right smack in the middle, on the crack between the cushions, and he is smashing down the ends of my cushions there. These cushions also are the T type and cannot be flipped. So... since you have a choice, I think I'd go with 3. As for the back... I plan to have a fully attached one next time so that it also cannot be smushed by kids and all.

Good luck!

3 cushion is my perference. The sofa in the family room only has 2 cushions and it is not comfortable to sit in the middle and it messes the cushions up when you do sit there. 3 cushions gives each person more individual space.

My previous sofa had 3 cushions and was ok. Nothing happened to it.
The new sofa I bought, has 2 cushions and it looks much nicer, more royal :-) For the time being 4 people are sitting on it occasionally and it's still fine. The back cushions are not attached, also two big ones. I guess it has to do with the quality of the sofa.

I have 2 cushions, detached. I like that they're detached so when they inevitably get flattened I can flip them.

Ok I will chime in I prefer two - here's why I am 5' tall and when I lay down my bottom goes down in between the cushions if there is 3. I would really prefer one long cushion.

I have a sofa with three cushions, one with two cushions, one with four cushions, and one with a single cushion.
The single is unquestionably the "dressiest," of cut velvet. The cushion is mostly down and feathers, and can be taken off (it has little elastic bands that clip to rings on the deck and this allows it to shift a bit but not slide off) and plumped up. At most, two people will sit on it---I think that is psychological. The two-cushion sofa seat really requires that you sit on one side or the other, lest you wedge down in between the cushions. :) The three cushion is an odd size, 81", and usually only two people will sit on it, at both ends with a sort of "no man's land" in the middle, lol. Our four seat sofa is more than 8ft long and comfortably seats four, but only three will sit on this one. Our designer always said that maximum seating is achieved with chairs!

I have both and prefer the 3 cushion couch.

I have had both. Currently, I have a 2 cushion, semi detached. My next sofa will be a 3 cushion, fully attached. I prefer them.

We have two couches of about the same size, one 2-cushion and one 3-cushion. People have no hesitation about sitting in the middle on the 3-cushion couch but never do so on the 2-cushion because they slide down between the cushions, while on the 3-cushion one everyone gets their own cushion. (And here's a LOL to rdsso - I'm 5'2" and when I lie down on the 2-cushion couch my backside usually ends up scooching down between the two cushions! THIS is why one should not be shy about giving a potential couch the lie-down test if that is one of the ways the couch will be used.)

One thing to seriously consider is getting a couch that does NOT have L-shaped cushions on the ends, so you can "shuffle" them to keep the wear even. Flattened cushions can also be re-stuffed; in the next couple of years we'll be having the seat cushions on our leather couch re-stuffed because they've gotten pretty squashed.

Interesting replies so far.
Seems most preferences have something to do with how many sit on the couch, that part isn't helping me particularly since the couch is mine alone. May help others in the future though.
I like tea-cushions (the L-shape). You can flip them from one end to the other by flipping them upside down but the middle cushion is always the middle cushion though you can flip that upside down too. Not quite as flexible as shuffling all three I suppose but I don't like feeling boxed in by a full arm.
rdsso and johnmari - since your not that different in height - I wonder if your couch/cushion lengths are significantly different?
I'm 5'4". I wonder where my booty would end up:) Not always easy to find a 2 cushioner to test.

I have a three cushion and I constantly do two things, I sit on all three cushions and rotate them all about once a month. My previous sofa was a t-cushion and it just did not wear well.

I much prefer 3 whether it's just me or other people. I don't like attached cushions for the simple fact that if I ever decide that I want to change the look of my sofa with custom slipcovers, I can't do that with attached back sofas.

I've had both 2 and 3 cushions. I recently replaced the 3 cushion one in my FR with a 2 cushion. I like the 2 cushion one better, not only for looks, but they seem to stay put better. It seemed that with a 3, one cushion always popped up when a person sat down.

I would avoid the T also since you can only flip them one way, and loose back cushions are the worse. I was forewarned and got then anyway - now I regret it. DH loves to slouch on it and the back cushion is always scrunched down. A hard back sofa is much more supportive IMO.

I prefer one cushion, it looks good but they are hard to find without being formal.

I have one in my master bedroom and one in my dining room. The one in my living room has two cushions and I hate it. I am going to replace it as soon as I can find what I am looking for.

I have a big couch and it's my most favorite couch I have ever had. The has two cushions which most of the time I like a lot. The only time I don't like it is if I want to nap on it. My hip hits right in the center of the two cushions and I sort of sink in there. Not too comfy! But except for that, I LOVE this couch.

{{!gwi}}

{{!gwi}}

marys1000, many factors affect how one person might find a piece of furniture perfect while another person can't bear even a momentary perch. WRT where one's caboose ends up when lying down on a couch, I think a great deal may depend on one's bodily proportions - my father was kind enough to bestow upon me a physique roughly resembling that of a gorilla (long torso and arms, short legs), while a long-legged person of the same height would probably have her bum landing in a different spot. When we were shopping for our last regular couch I didn't find it that difficult to find couches of more or less the correct size with different cushion styles to test out, although they may have been so ugly that you couldn't have paid me to have them in my home, and I don't exactly live in a shopping Mecca. The sectional was more difficult since we needed an odd size but we lucked into a local store that had it - in a really hideous fabric and the backwards configuration but it still got the job done as far as the use-test was concerned.

Also, a cutback arm gives the benefit of the square, easily-shuffled seat cushions without the boxed-in effect of the full-depth rolled or square arm, and it's a classic, pretty look. We chose a cutback arm because it made the total piece look less massive than a regular rolled arm did (we have a pretty small LR) as well as the convenient square cushions.

I do like the single-cushion camelbacks newdawn1895 posted - I have a nice camelback couch, currently with two cushions, that is on the "when we can" list for reupholstery and it would definitely look nice with a single cushion, and with the right fabric we could change the formality of the shape into something more appropriate for a country-style kitchen. One good thing to have with a single cushion is an anchoring clip at each end since I remember one couch of this sort where when you sat on one end the opposite end of the cushion sort of curled or popped up. I do like the tight-back style for neatness although it's not quite as cuddly; the incoming sectional does have attached back cushions but as Mick says, "you can't always get what you want" :-) and it was certainly better for us than completely-loose back cushions. (Although my leather couch has back cushions that are "attached" by velcro strips, which I like.)

To be persnickety, a T-cushion has the protrusions (sometimes called "ears") on both front corners of one single cushion, while an L-cushion only has the protrusion on one corner which creates, obviously, an L-shaped cushion. example diagrams

Like several others have reported with a 2 cushion couch, when 1 DS uses it he has a tendency to sit in the middle, which is causing the cushions to gap and scrunch up away from each other, which causes me to flip them just about every day. In fact, it's on my list of things I hate about my Macy's sofa.

I like 3 cushions, attached back. The attached back makes for easier time making sofa look nice....the 3 cushions create more comfort level if you have more than 2 people ever sitting on your sofa.

Red

I went from three down to two and hate it

Not versatile for moving around for wear and tear is the main reason, but it also makes the sofa look entirely less comfortable