I have those windows too, I did not build the house. I agree with what GNBuilders above said. No real advantage or disadvantage. Just the style of the house. At least, they don't leak.

I would have put in much bigger windows.

Primary disadvantage is going to be price. Most times they will only come in very standard sizes as well and operability is limited.

Unless they suit the style/elevation of the house, they look like port holes. That don't open. And that is what those look like. Fine for a ship.

Much nicer here..........

My window is in the dining room so you also get a nice view from the second story hallway/loft which is overlooking the dining room and the other one is mirrored on the front of the house above front entry door so when you walk into the house this is the view

I think they tend to look nicest in context (Shingle style, Victorian, or other architectural styles that lend themselves to it). And sometimes can look a little silly in poor context. Or, when misused on the front of a facade, like eyes! :-)

I will also admit that every time I see round windows (or barrel vaults, or eyebrow windows, or anything with lovely sinuous lines), I can hear Dad's voice: Curves cost. This is what comes of being raised by a carpenter.

Hello
Here it’s the similar round window with custom wood panel around . This has been done for one of my client , they are so happy and glad that they trust me about the design.
Regarding how much cost them , actually the window itself cost about $2200 and the wood work for around it , cost them almost $1500 ( don’t forget the price is in Canadian dollar) .
I hope that was helped.
ALEX

Here are the photos that I forgot to add the on my post , it’s before and after pictures.
Thanks again
ALEX

BY THE WAY ,you might see a temporary platform in the “after” picture which it supposed to be built to be able to work on it which it removed as sold as the top section has been because as you can see , the window wasn’t on or near the ground , it was start about 10 feet high from the ground.