I have a 2 1/2 year old and a 4 year old. We use the Peg Perego Twin Aria and love it.
It is very lightweight and extremely easy to fold. It fits into single doorways, though some are tighter than others. When this is the case, the best trick is to angle in the doorway one way, then once your in, angle out the other way (like the letter C.)
It is also good for us because the seats recline pretty low for naps and they have little trays for snacks (no drinks though). The hoods are separate for each child and the basket below is quite large.
In some stores and areas, it is a little harder to get around because they like to jam the aisles with stuff, especially during the holiday season. But we really haven't had too much of an issue.
I did a lot of research before purchasing this one. It really depends on how you're going to be using yours. We did not want the tandem (like the very popular graco duo glider) because though it is narrower, it is very heavy and hard to get in and out of the car. We also didn't want the boys fighting about who goes in front.
Good luck with your search. Hope this helps!
Isabelle