I used a reversable car seat (the same car seat) for all three of my children.
We are now buying a capsule for baby number 4 (our last baby).

Capsules are just more convient. The reason we have decided to go the extra expense this time around is because the capsule can be used with my P&T's pram, which is going to be ALOT easier for me when I have to do anything with the kids. In particular with school runs on rainy days (we have to pick up directly from the classroom on rainy days), it means I won't have to wake bubs up to get all the kids out of the car to go in the school to pick up my DD. Considering school runs tend to be right around the traditional nap times of my kids, this will be a lifesaver. The capsule we are buying (s'n's unity) goes up to 12kgs - which is about 1yr old. Most capsules will only go up to 8-9kgs. We still have the convertible car seat for bubs to go back into once they outgrow the capsule.