D.S.
Shannon,
Most convertible carseats will not fit a newborn correctly, despite their claims. (Unless you are a momma who has 10+ lb babies!) Some kids can't fit into the convertible seats until they are closer to 4-6 months old. (depending on the size of the child)
The infant seat is made to fit newborns and smaller infants. I would definitely go with an infant seat for the first few months and then looking at a convertible seat. I highly recommend any carrier with a FRONT harness adjuster (the Graco Safeseat and Chicco Keyfit are two of my favorites!) this will insure that your baby is harnessed in properly each and every time.
If you have any other questions about car seats feel free to private message me!
(I am a certified carseat technician)