Re: combi coccoro or chicco keyfit 30?
I have a coccoro my short 20 month old still fits in and it's a great seat for travel and easy installation, but I loved being able to click my infant seat into the stroller so I didn't have to wake the baby up to pop into the post office for 2 minutes.
I originally bought a snugride 22 for DS1 b/c I thought I wouldn't want to use the bucket once he got heavy, but the ease of clicking it in the stroller and being able to easily cover him with our cold midwest winters (we have street parking only and sometimes have to walk a couple of blocks) was just so great that I upgraded to a Snugride 30 to keep him in the infant seat until February or March when it started to warm up.
If I had an attached garage and didn't run so many brief errands with the baby in tow, I would definitely consider skipping the infant seat.
It really depends upon your lifestyle and your child. My DS always woke up when I took him out of the car seat, but lots of babies sleep right through being transferred in and out.