You are referring to the infant car seat (a carrier is like an Ergo/wrap/sling/etc). Check out this link, all the current stats for all the infant car seats are listed there.
Which Snugride are you meaning, the Snugride 22 - weighs 7.5lbs, holds an infant to a max of 22lbs and 29", or the Snugride 35 - weighs 9.7lbs, holds an infant to a max of 35 lbs and 32"? Obviously, the 22 is a lighter seat, but the cons are it will be outgrown sooner, and the features are basic. I prefer the 35 because of the lock off on the base and the front adjust on the harness and the longer harness straps (just to name a few things).
What is it you are looking for in a seat (aside from weight)? Are you going to be using it with a stroller (and what brand)? What type of vehicle do you drive? And what's your budget?
I have to P & R, but if I don't catch your answers, katcarls can help.
Also, the linky I posted is also a forum hosted by car seat techs, they have all the answers!