2.5x is useless to me. I started there then went to 3.5x. Now switched to Exam Vision which are 4 way changing going from 3.5-6.5x. Best loupes I have ever had! I do almost everything at 6.5x, from restorative, endo, surgery, suturing, etc. Going to Perio and will continue using 6.5x. It is hard to downgrade in magnification, when you are able to see very fine details why would you want to go back to seeing nothing ie. 2.5x. Not old, under 30.
Don't worry about "most" dentists, find the dentists that impress you and emulate them.