I guess it also depends on how much money you have to spend. We didn't really have the funds to have both a capsule and a car seat later (even though you can hire capsules fairly cheap through the council). So we opted for the convertable car seat. Especially since we knew we were having a long baby and felt she wouldn't be in the capsule for long. We had no problems getting her in and out of the car and we were lucky she often stayed asleep during the shift (I have a friend who used a capsule and her baby still woke when she was moving it in and out of the car).
If you get a good quality convertable seat, they can be just as safe as the capsule (IMO). I also have concerns about leaving babies in capsuels for long periods of time (in one go) because I have heard it can damage their backs... and since I've always had a tempremental back I wanted to try and avoid that for DD.

HTH - good luck making your decision!

MG