Well, those are very good questions, and I will try to answer them one at a time. First, we need to assume that the outside diameter of the tire will be the same regardless of wheel size. This should be the case, the only difference here would be the inside tire diameter (wheel size). first, top speed, Top speed will probably not be effected by wheel size choices, again, tire diameter will be the same regardless, so the overall gearing (a combination of transmission and tire diameter) will be the same for both. With acceleration, the issue is weight. A heavier wheel+tire combination will accelerate more slowly. Basically, the more weight the engine has to accelerate, both in total vehicle weight and rotating weight will be effected. Again, weight lost on a 15 wheel, which is lighter than a 17, you will gain it in tire weight. Is the difference exactly the same? Maybe, maybe not. You should regardless get light weight wheels if possible, and good tires. Ride quality is something you will definitely notice a difference between the two sizes. Your wheel and tire choice will effect your suspension, please again realize overall diameter of the outside of the tire will be the same for both. Your tire acts as a spring and damper, and on larger wheels, the tire thickness (basically the distance from rim to road) is smaller. Lower profile (thinner) tires tend to have a stiffer casing, and will provide a stiffer ride. Smaller wheels will give a more compliant ride. The reason for this is the casing is softer on a thicker tire. Essentially, the thicker the tire, the more distance the tire can compress when acting as a spring. If the roads near you are horrible, maybe 15s are better, but from I have seen, even with 17 inch wheels, there is plenty of side wall to the tire. As for cornering, weight counts, as does what was just mentioned. A thicker tire (higher profile) has more room to wiggle around, and therefore may not handle as good as a low profile tire (17 inch wheel). Again, you want the lowest weight wheel tire set up possible, because your suspension will react better when it weighs less. At the end of the day I can tell you that the trend over the last few years has been to go with ever larger stock wheel tire sizes. Much of this is because of looks. Some because a larger wheels results in thinner tires, and gives much more feedback. I drive on 15 inch wheels in the winter, and 18s in the summer. My 18s though are very thin, and thinner than the tire on a factory five 17 by far. I have to be very careful when driving to avoid pot holes. But the tires I have are great, and provide a much sportier feel than the other tires I use. My suggestion is to determine the tire widths, because more tire is more weight, but also a bigger contact patch, so you get better traction. I imagine with such a light car, that is very fact, you may want more rubber than less. And from a quick search online I can tell you that more high performance tires come in the 17 size you would want than the 15 size. Additionally, a 17 wheel will allow you to run a larger brake kit. Hope this helps.