With the Trophy Hunter front zips, if I don't have a shirt tucked in underneath for whatever reason the little buttons pinch my skin if I bend over.
For that reason alone I prefer side zips, but otherwise don't mind either.
I have the same problem! And I wear a kids 16, so it's not like I have THAT much to get caught in there! Unfortunately as far as schooling breeches go, pretty much all the cute ones only come in front zips now, so I suck it up and just tuck my shirt in. I also get the weird zipper pucker on some of them, so for shows it's side zip only!