Haven't ever used a drawer, but you too can notice that dishdrawers have square racks as regular 24" DWs

18" diswashers are a compromise for very small kitchen. I mean : draw the biggest possible circle in a 24" x 24" square, then the biggest possible circle in a 18" x 24" rectangle.

You can see that corners in the square are closer to the circle, while rectangle ones are not that close
Spray arms draw a circle while spinning.
So the spray action in rack corners is more effective in square rack designs (DD and 24" DW) than rectangular rack design (18" DW)

If one is aware of this and loads a 18" DW consequently, there's no problem.
But if you load tall and narrow juice glasses soiled of orange juice in the corners of a rectangular rack (18" DW), you can't pretend the will be cleaned as well as a dishdrawer or a regular 24" machine do

Anyway a single drawer holds less items than the two racks of a 18" machine
A regular 18" or 24" machine is more flexible than a double dishdrawer : in case of extralarge items you can raise the upper rack or even take it out (Bosch), with a dishdrawer ... you can handwash.

I guess space is not your issue (a single drawer is as large as a 24" machine), rather you aren't supposed to have a daily full load in a regular 24" DW
In this case be aware that latest european 24" DW have load size sensing devices and use 7-8 litres of water (round 2 gallons) for a *full= two racks* load. The *single* dishdrawer uses 1.95 gallons per load, so partially loaded 24" machines can even use less water than a *single* drawer.

To cut a story short : if you have place go for a regular machine : it cleans better, you'll have plenty of place for those times you have guests at dinners and on the other side you can run partial loads without feeling "guilty"

you can get a cookie tray in the 18" , darn near impossible with anything else in a single drawer./>Nonsense. A 12"x15" cookie sheet in a DishDrawer, with a 11" skillet and lid and several other items, including some things not seen behind the sheet and under the plastic container at the front right. I could get in a bit more with more careful/structured loading ... but didn't need to, had just these items to be finished.

Assessing the photo above and my friend's DDs, my 18" Miele will hold more than one DD, esp. due to the 3rd rack. I have not had any problems with items not getting clean.

Of course a full-height double- or triple-rack unit should hold more than a single drawer ... but neither is the pic above a maxed-out drawer. Both drawers of a typical 24" wide double-drawer DishDrawer fully/properly loaded likely would hold more than an 18" machine. There are no 18" width DishDrawers for tight horizontal space considerations, but there are single-drawer units for vertical space considerations.

Water use per drawer depends on the selected cycle. At 0.8 gals per fill, my DD603 (6.5 years old) ranges from 2.4 gals for the Fast cycle (wash-rinse-rinse), 3.2 for Normal/Eco (wash-wash-rinse-rinse or rinse-wash-rinse-rinse), 4.0 for Normal (wash-rinse-wash-rinse-rinse), to 5.6 gals for the Heavy cycle (wash-rinse-rinse-wash-rinse-rinse-rinse). 1.95 gals quoted on the newest model is likely the Fast cycle with redesign on the mechanism for lower water consumption.

DishDrawer loading examples

Thanks all for the info. Does anyone know where I can get the water usage for all dishwashers?

Some pictures of my grandma's 18" Miele dishwasher.

Alex

Here is a link that might be useful: 18 inch Miele

I'm looking at a single drawer dishwasher to be our only dishwasher. There are just 2 of us and we don't put big clunky things in our full sized dishwasher anyway. Only glasses, silverware, dishes, soup bowls. I have the space for a full size but I don't like bending down to load and empty it. Just like I'd rather use a wall oven than one under a range. Would appreciate anyone's personal experience with one or opinion of this option.

When I did a thorough study of 18" DW in 2008, some of them had a 1/2 load cycle. It's practical for people who have small loads. In my opinion it should use less soap too. But, all things considered, it isn't a big thing either way. In terms of water savings or other savings.

hiroman is generally right about most or all of his comments, if I reaqd them a certain way, in a certain context, but I also know that people who have 18" dishwashers are all happy. None have ever written in gardenweb or other forums to complain in any way (after searching I have found no complaints.)

hth