I have a Mini 14, a S&W M&P15 and Colt LE6920 and have put thousands of rounds through them. I like both platforms and all offer features which I like/dislike.
I think the Mini is fun to shoot and I love the nostalgia associated with the platform. I do shoot my AR's more often and feel more comfortable with them when running drills etc, but that's just me.
All of my guns are capable of performing at a much higher level than I am able to achieve.
You really can't go wrong with any of the major brands listed here in this thread. Good luck with your purchase.