[Ammunition]

I'm new to the realm of wheels, tires, etc - I've learned a lot from this forum and general interest, but I could use some help in deciding wheel size.

My car is primarily is for spirited, or weekend driving. I haven't found any wheels I really like yet until now (the new Gramlights 57Transcend), but they only come in 18" +

I would like to think that if I am going to buy new wheels, that I am at least gaining some small performance upgrade, and not simply a cosmetic one; I will probably still be saving weight with these wheels, but I really don't know what difference the 18x8+45 or 18x8.5+45 (same offset) would make for me, besides the 8.5 being a wider contact patch for slightly more grip (but does that come at a cost to acceleration, etc?)

Basically for a car that isn't tracked, I need help understanding what difference I could expect from the 18x8 vs 18x8.5 (again, offset would be the same as these only come in +45)

I've searched, and googled multiple times, but I haven't really found anything that specifically answer my question for someone that has only a very basic understanding of wheels, and tires.

Thanks very much for anyone that can enlighten me, and help me make a decision between those two (note: I'm not really interested in other wheels, and therefore sizing - I would simply like to understand the differences I can expect between these two should I choose one over the other).