I'm not a fan of muesli, my first pigs were on that and I gradually got them off it. I was much happier with the choice of Burgess.
Well my experience is that it really does depend on the piggy. You can always try at the end of the day. I've had piggies that won't swop over and I've had piggies that instantly want to swop over. At one point I was feeding burgess excel mint, burgess oregano, bunny basic, & hey gates pellets.... I've put the two types of food into one bowl and gradually lessen their old food choice until you eventually have your chosen food. Of course, if they aren't eating the new pellet, you don't want them to lose weight or go off their food (unlikely), but it's always worth keeping a close eye on whose eating what food as well.
So with two piggies, means two bowls as well to stop any squabbles.