Which is safer: infant or convertible seat?

[alirebco]

I'm not sure if I am going to leave my son in his infant seat until he outgrows it since we are considering giving it to my SIL who is due in September. He would be 9 months at that point and I was hoping to just move him to a convertible seat - probably the Britax Marathon and continue to have him rearfacing until he reaches the rearfacing limits on that seat.

Is there any argument to keeping him in his infant seat - the Keyfit - until he outgrows it other than the cost of buying him a new seat sooner? I wasn't sure if it was safer to keep them in the infant seat as long as possible before switching to the convertible and I haven't been able to find any information about this topic. Would love your thoughts!

[Joolsplus2]

Any properly used seat is safe :) (ie, no difference between an infant seat and a rearfacing convertible). Lots of parents use conertibles from birth or just a couple months old because they like them better, and by 9 months he'll definitely fit in a convertible safely (and be sitting up, too... infant seats are pretty handy before your baby can sit well in grocery carts and highchairs).

:)