15" vs. 17"

['74super]

what is the main advantage of running larger wheels? couldnm't i just buy an aftermarket 15" wheel and put good tires on it? i found one that i like and will now proceed to locate good directional racing tires for my bug. and 17" tires are soooo expensive nowadays. would i be able to pull off good handling with a 15? i can't go to 17 because of $$ issues..i'm still in high school. thanks for all the help.. -nick