I have often mixed brands front and rear, I don't like to but sometimes I have to. It can make the bike feel odd this could be real or just in your head though. Some mixs seem to feel ok and others have felt like I would die LOL.
If you don't HAVE to do it then don't. But if needs must then try it, if it feels ok then great but if it don't feel right then don't carry on risking it.