Well it depends..obviously i dont know how you drive your car, everyone has there preferences, most people like to balance style with pace, whereas id rather have 2 sets of wheels to fit both criteria!
How many problems did you have with 17s on, surely 16s wouldnt be a prob? The main thing which is empahised is the valvers lack of torque, most 16 inch tyres only go down to a 45 profile anyway so the 15s will be better for accleration even if you got some very fat tyres! 15s will always look bigger if you slam it..but everyone prefers 16s..hmm..basically just think about what you care about the most and then make a decision based on that? Pace,style or both?
-Rob