I'm a big fan of radians as those are what my kids are in, but there are also other great options on the market now (when I was buying there were fewer options that kept a larger kid RF for a long time). The radian can be a little quirky to install and takes up a lot of room RF until a child is old enough to use the angle adjuster (have to be able to sit independently) but is a great seat otherwise and I'm a fan.
The First Years True Fit is a great seat. The only complaint I hear about it is that there is a 35 lb weight limit for RF, so an all around bigger kid might have to turn around sooner.
The graco size4me70 is supposed to be very good as well and is taller than a radian
The Clek Foonf is really cool, but very expensive and huge.