I have tried the foonf, nextfit, and peg perego (I previously used the b safe for my girl and after much grief, have learned to love it when I finally realized what I was doing wrong).
we got the foonf for my car and were searching for an easy to use and good convertible carseat for grandma.
i may be in the minority here, but I absolutely dislike the nextfit. even my husband who generally likes any carseat I get because it is one less task for him also hated the nextfit. it was the only carseat he had ever asked me to return because the harness adjuster (to tighten the harness) was nearly impossible to use. there were times when we failed to properly tighten the harness, so I had to question the utility/safety of the nextfit as a carseat for our family. both the foonf and peg had amazingly easy to use harness adjuster (even easier than an infant seat!).
among the seats, the nextfit and peg perego appear to be comfortable because of the cushions. the foonf has the least amount of cushion, but since my daughter graduated directly from an infant seat (which has minimal cushion), she was quite comfortable in the foonf.
also, my daughter hated the harness pads on the nextfit. she actually grimaced, struggled to pull them off, and cried at times. the foonf harness pads are the shortest, hence most comfortable for her. we had to take off the peg harness pads (which is okay by the manufacturer but is not an option for the nextfit) because they were long and interfered with the chest clip placement for now (we will replace them when she grows up some more).
the nextfit provided the best lockoffs for installations with seatbelt. the foonf lockoffs popped frequently which rendered them useless (but now you don't need their lockoffs anymore and can safely use your ALR in your car for a good seatbelt installation). and peg perego comes with a locking clip (which is useless and nonfunctional given that I cannot get a good install with locking clips). however, all three seats can be installed with their own latch system.
the nextfit and foonf equally take up the same amount of space (in terms of front to back of the car) when rearfacing and the peg perego takes the least. the nextfit is the widest seat among the three and takes up a good deal of space.
I am still puzzled by everyone's love for the nextfit...I guess it must be because the keyfit is so sensational that chicco has this strong and large group of loyal fans. I would never recommend the seat for anyone...especially for grandma. I contacted chicco to see if it was a user error or a manufacturing defect of the product, but nothing helped. yes, I was quite sad to return it since I loved the Gemini color, but really, it was just going to collect dust as none of us wished to use that seat in our car.
grandma loves the peg (it is easy for her to use)...just as she loves the foonf, but the peg is lighter and easier to transport if needed. I love both the peg and the foonf, but because the foonf has the higher height limit for rearfacing (my daughter is tall for her age), that was naturally my pick. even though it's so costly, my husband thinks the foonf is worth the price (prior to my purchase, he couldn't imagine any carseat would justify that price).
in terms of rearfacing height limit, from shortest to tallest: peg, nextfit, then foonf
in terms of weight limit for rearfacing, from least to greatest: nextfit, peg, then foonf
mind you, I have only used these seats rearfacing. so if your purpose is to rearface and those are your only 2 choices, I would go for the peg. but as other posters mentioned, your child would soon outgrow it. so i'm throwing the foonf back into the mix for you as I really like that seat. I heard the radian is quite a good seat for tall kids too (I haven't looked into that seat since there seems to be mixed feelings about that seat).
