I brought both my boyy a weatherbeeta meh combo each and both slipped back and rubbed so then I brought both an Amigo Bug rug but my youngsters was torn in about 8 places in 3 days (due to the others pulling it... however the weatherbeea 1 didnt even fray) and rubbed his chest and my other horse has rubs from it within 7 days and also the straps are coming off, not impressed, especially as he is really easy on his rugs so its made badly!
I have since brought my young horse a derby house one which fits fab, but he's not had chance to wear it yet as I waiting for the sores from the other rugs to heal!
I have the greenguard grazing muzzle, wouldn't use anything else it doesn't rub and it works really well with my big horse and he also has a Derby House Tego Fly Rug with mask as he hates the heat and it keeps him really cool.
I have used greenguard muzzles on mine for years, they are fitted correctly, there is no rubbing & my horses are in great condition & can stay out at grass all day without putting on masses of weight or the risk of laminitis.
Some muzzles can rub, any ill fitting tack can..... so fit the things correctly!
As you can see I think muzzles are really good & do a great job. The main issues with muzzles are horse owners who have strange idea thinking they are cruel
& would rather risk their horse/pony becoming overweight or laminitic?