For performance reasons and money 15s are the best to go with.
Many tires to choose from and rims, while at affordable prices.
16s are fine too but because of the lack of choices with tires it becomes a PIA.
17s are sometimes needed to clear some brake kits but over all a 17 tire weighs a decent amount and then 17inch rims are also heavy unless you are willing to spend money to get light weight. and the looks of a 17inch rims and tire just does nto appeal to me.

good luck.

I use a very simple setup for street and track
street- 15x 6.5Rota SS with MXs
track - 15x 7.0Kosei K1s with various Rcompounds- Now I'll be using RA1s and when they are done I have Victoracers