If you play a 7 1/2 ips at 3 3/4, you'll definitely hear a difference. Bada bing!
Okay, now that I've gotten that out of the way for all who follow, if high fidelity is your quest I wouldn't even bother with 3 3/4 ips tapes. Which causes me no end of head-shaking when I see the prices that some 'pop' commercial tapes go for. I can only assume that the buyers are discography completists, uninterested in actually playing the tapes. Or at least, that's what I'm hoping.