My daughter and I saw both over the Thanksgiving holidays. We were pleasantly surprised of how much fun we had at both. A lot would depend on you and your own tastes. School of Rock had lots of kids at the show (lots of them boys), the show is good for families. The lead is charming and does not do a direct Jack Black imitation, but does portray the character as a lovable loafer. The kids are very talented and shine as the prep school kids becoming a rock and roll band. The ALW score is not your typical ALW score. My daughter is not a ALW fan, but liked this score. We left humming a couple of the numbers. I would recommend this if you have kids or are a child of the 90's.
On Your Feet was my favorite of the two. I loved Gloria Estefan when I was in college, so I am a fan of her music. Actual m embers of the Miami Sound Machine are in the orchestra and the sound was authentic. The book of this musical is much better than Beautiful. The show is solid. If you are a child of the 80s and a fan of Gloria, I think this will be the show for you.
Overall, both of these shows are solid, fun, and entertaining shows. They are not Pulitzer prize contenders, but are well crafted.