Squareback vs round back alternator?

I rebuilt my 318 like 15 years ago and have put on 8k miles in that time. I replaced the alternator at the same time and recently the bearing went out on me. Seeing how alternators are relatively cheap I was just going to replace it. But when I started reading it looks like there is much against the newer (I assume mine is one, Oreilly) square backs but I don’t really understand the issue? Mine has always done well to keep a charge and I’ve ran it at night. Just wondering what I’m missing out on before I make a bad purchase.