Check out this blog: http://carseatnanny.blogspot.com/
I think her comparisons of different carseats are really interesting! I didn't find the blog until I had already purchased my MyRide65 (which I LOVE) but it is still very useful.
I recommend you stay away from the 3-in-ones. We looked at some, but they seemed uncomfortable and too upright, and since a booster seat only runs about $25 anyway, we didn't think we were saving that much money. I have heard good things about Britax, but we didn't have $200-$300 to throw around (especially since we wanted to buy two seats - one for my car and one for my husband's). The MyRide65 is awesome. We used a BRU 20% off coupon for it, and so it only cost us about $130. It is side-impact tested with wings, it has cup-holders, is good rear-facing up to 40 pounds and forward-facing up to 65. My son is also very very tall - in the 92nd percentile at 16 months old, and he fits comfortably rear-facing. His legs do cross, but he doesn't mind. The only downside we've found is that it is a very wide seat, which is probably good for comfort, but not good if you're trying to fit 3 seats in a small car or something like that. In my van, absolutely no problems.
I would also like to recommend AGAINST the Graco Comfortsport. We bought that seat with our credit card points when my son first outgrew his snugride (he was about 7 months old!), and it's just not as good a carseat. The chest-clips felt flimsy (the same thickness as the snugride, but the baby is so much bigger now!), and getting it tight and level in the car was really difficult!
Good luck!