My .02...
I had a Mini, HAVE a Bushmaster AR-15. Depending on exactly what you want it to do, get the AR. If you want to trick out your Mini, every accessory I ever bought for mine said "181 or later". Mine was a 183, so it was fine. There's no point in owning a 'pre-ban' if you can't fit the stocks you want on it.
Also, I was never able to make the hi-cap mags for the mini work. My Bushmaster works with all but the Orlite mags. GI mags are still quite available, and they work. If they don't, Wolff has a kit to spiff 'em back to spec+ and they work again.
I have always felt that the Mini line of rifles had "personality", and that the AR-15's really don't. (I truly believe that "The A-Team" would not have been the show it was if they had used AR's instead of Mini's)
Anyway, I do love the little Rugers, and will probably own another one, but a Pre-ban 180 series would have too many negatives for me to even consider buying it.