same, that's why i will most likely go with a set of Rotas.
personally, i would go with the 16x7 but if you get the 15s i would recommend the 45 offest.
i like the tires that are available in a 16 if you run a street tire. race tires are another story.
Edit: gearing is a big factor in choosing a wheel too. with my stock 17s it was hard for me to decide weather i wanted to shift or keep it in 1st. WD told me that a 16" wheel with a 45 series tire would help with that. i'm sure another season of working on my driving will help that as well!