britax is the most padded and comfortable for your child. I had the chicco infant carrier and hated it because the paddidng wasnt breathable so my baby was always sweaty. I now have the britax Boulevard and love it because it has the padded headrests on the sides so my toddlers head doesnt slouch over when he falls asleep.
I am a car seat technician and I have seen and been through a LOT of seats. They all have features and drawbacks, you just have to think about what features you want and need. They all are safe because they have to meet the same federal standered for crash testing.