Hi! I just answered this question in a private message to a mama. Here is what I said:
I ended up getting the Nextfit from BRU. They have a 20% off coupon and an extra 10% off if you sign up for their credit card making it a good deal. (a hundred or so less than the Peg)
I drive a Toyota Matrix. I'm happy with the fit front to back. I can put the passenger seat in a comfortable position and slightly recline it. I am 5'7". The Nextfit has 9 different reclines, 3 to choose from for RFing. I have it on the 3rd one (more upright) and it fits good and she doesn't have any head slump when she sleeps. She is 18 months old.
It is quite wide, but we aren't expecting any more kids. (so might not be a good choice if you have twins, I don't see how two of these would work side by side in a small car unless you put both outboard.) It is quite heavy too, heavier than the Peg so that might be a consideration if moving it a lot. I can move it just fine though.
The fabric is weird and is made of something that reminds me of a wetsuit. She spilled water in it and it just pooled up and stayed that way for hours till I soaked it up with a towel. The Peg is suppose to be breathable, and I like that since we live in the desert. I'm not sure about flame retardants, but the Peg is certified to be safer than most seats... not sure what that means, they both still use harmful chemicals. No way around that. It could just be a marketing scheme.
The harness system is nice. I can easily buckle her in and out.
The best thing about the Nextfit is the install. I'd get it just for that reason alone especially if you'll be moving it a lot. It literally takes seconds to install if using latch. We use a seatbelt install because we can't use latch in the center of the backseat. The seatbelt is a easy install too. The Peg is suppose to be easy to install using latch, but not seatbelt... something about the seatbelt path is too narrow for your hand to fit through on the Peg.
So for the install alone, if you have to use the seatbelt, I'd get the Nextfit. If you can use latch, either one should be a breeze.
I'm happy with the leg room she has. It doesn't look like it ill be a problem when she grows. The harness straps do seem to be narrow and I wonder if they will be uncomfortable for her around her neck as she grows... but I think they might get wider when you make it taller for bigger kids.
The Nextfit does make her sweat, and the back of her head and back is a little wet when I take her out... but not as much as her Graco infant seat, so that's an improvement. The Peg is suppose to have great fabric that breathes. I wonder if anyone can attest to that on here? I'd love to know if their kid gets sweaty with the Peg too?
A friend of mine drives a Prius, which is a small car and she is happy with her Diono Radian with angle adjuster. I like the Radian for its slimness. The Nextfit is huge width-wise and I wouldn't get it if you need to put another seat in the back of your small car.
Good luck and let me know what you get and how you like it!!