I've had 3 x 3.75" CRs since 1987. 1st was a 2nd hand APR (grey colour). Used it for Oz instrument & ATPLs, & US ATP. At some point in the mid to late 90's I left it in the car one summer afternoon & it softened & bent along one edge when something rested against. I finally got sick of the bend and replaced it with the same sized Jepp (also grey). Pretty sure that was the one I used for my UK ATPL in '99.
A couple of years ago I replaced it with a 3.75" APR (now only sold in yellow. I think it gives better contrast so minor yay, I suppose) when my Jepp had become rather scratched & worn. Can't say I've noticed any significant difference. The hub is slightly different and I'd rather my new APR had a bit more friction to resist rotation, but other than that? Nothing I can think off.
A friend recently borrowed my APR CR for his FAA IR theory, and my old Jepp was put back to work.
All my CRs have been the smallest 3.75" size. I like the smaller size's easier fit into clothes & backpack/bag pockets. I've never had trouble getting accurate answers from them in all those exams I've done.