I've never tried any kind of guard. I got kicked in the stoma when my stepdaughter was 5 and I survived that without any damage, so I haven't felt the need to buy a guard. I bought the stealth belt when I first got my stoma, but didn't like it at all...the way my bag had to be put on sideways didn't work for me - it just made my stool pool around my stoma.
Sorry this hasn't been more helpful!