I have the Graco DuoGlide which I loved...especially when the younger one was tiny because you could put the Graco infant carseat in the front ot the back. I would stick ODD in the back if I were going to a store (so she couldn't grab items off shelves!) and would put her in front for outside walks so she could see what was going on. It folded up easily (I can do it with one hand if I'm in a bind) and fits in the back of my van fine. Only downside was canopy for front is kinda flimsy so I just draped a light blanket over if it was really hot that day. Also only the front has snack/sippy cup tray...not a big deal when they are younger either. Front seat can be upright or reclined...and back seat can be upright or all the way down...no inbetweens. Storage bin is hard to get to if back seat is fully reclined, but is very large and holds lots! All of the things I mentioned would be nice if they fixed but weren't deal breakers for me and I would definitely buy it again! Best decision I made as I almost debated trying to make due with a single stroller...but have gotten SOOO much use out of the double!
As YDS got a bit older, I got an Instep Bike Trailer to pull behind my bike, and converts into push stroller as well. I particularly like this (once younger one is old enough to sit up well) because the kids sat side by side and could interact, plus it had a build in weather sheild if it was too windy or sunny that day. But wouldn't take this one to the mall or anything.
I bought my Graco Duo for $110 or so new on sale, and the Instep Trailer at a garage sale for $40. I agreeto keep your eye out on craigslist for sales...I see them all the time on there! Or if you were like me there wasn't alot to buy for the new baby...so it was fun to pick out a new stroller.
If I had to just get ONE style though I really like the front-to-back seating for a more anywhere, everyday stroller. Hope this helps...happy shopping!