Depends what you want.
I like 16s and can confirm that with narrow coilover conversion RBR 16x8 +10 fit with stock arches and 225 tyres, anything that brings the wheel further to the outside of the car than this could potentially lead to the need to run 215s although you may get way with a 0 offset.
Usually more choice in 15" by the way but I prefer 16" and need it to clear my brakes.
Good tip, don't use the forum search, use google using hybridz.org at the start, always gets better results. I searched when I was a newbie and it took a lot of time, but the answers are there. Just make sure to check more than 1 source, ideally more than two.