Hi There!
I was going to go for a capsule (we got given one but it was too old and didn't have a 5 point harness). In the end I decided to get the convertible car seat and it works well for us. Some people rave about having a capsule, but most mums say they are just too darn heavy with a bub in them! (After Flynn was born and even now, 2 months later, I feel very weak and have trouble lifting heavy stuff, plus you're worn out and sleep deprived!!)
In regards to hire, I'm sure that hire companies would be very strict about knowing the safety history of their equipment, so I wouldn't be worried about that. HTH
Catherine