I can tell you what I mulch with and I will probably get some blowback. I have been trying to grow ericaceous plants for years now with hit and miss success. It wasn't until I started mulching them with plain peat moss that I am finally having much better results. Yes, if you let peat moss dry completely out it is very hard to rewet it. But I don't let areas with these types of plants dry out completely anyway. I put down about a 2 inch layer and bring that out to at least a foot, usually more, past the dripline.
Another advantage to this is you can peg down some outer branches and they will root into the moss making a fuller plant.
YMMV.