I like Chico's infant basket seat a lot, along with the caddy system that you can just bring a small light stroller with you. Graco's usually made out of heavy steel and their "system" are not easy to use and weight a ton, but Graco's front facing back supporting boosters are designed well. IMO Britax is only good if you want those extra side protection and you never wants to remove the seat ever. They are heavy but they seems to be overbuild and not user friendly. Yes, I buy a lot of used car seats (I check them thoroughly and I usually buy the best used seat in each category after a lot of research on what works for me), and I would never build those one size from infant to booster, they all have too much compromise if buying that way.
Also don't forget how easy it is to clean the seat. They will need to be cleaned because babies have accidents. I loved my Safety 1st but they were pain in the butt to take apart and clean.