I always like the ones that fit my pot. I can pour the water out and it catches the pasta or what ever. Now that I don't cook a lot I like the small ones. You need to think of where you are going to store a big one. I did not know they made them that spans the sink. I would not want that unless I had a very large family to cook for.

I got a sweet white enamel one at Ikea for $10. The bottom isn't fully rounded but you just have to tilt it to drain the little bit of remaining liquid out.

I just purchased a Kraus Colander that spans the sink. Still in the process of finishing up my kitchen so haven't used it for anything but washing fruit. It's a bit on the expensive side but looks nice but it's also on the heavy side. It comes in different sizes to fit sink size. I also purchased a couple of inexpensive square colanders with handles, one green and one white by Joseph Joseph at homegoods.

Here is a link that might be useful: Kraus Colander