I agree with mpo. Batting is cheap, comes in low and high loft and is washable. It comes in sheets as well as for stufing. Felt is stiffer and probably thicker.
Bought a compacted type batting yesterday, now realise that the felt is a bit thicker,and makes a better padding. The instructions from "Moose", where I bought the design, specifies that felt should be used, but I realise it can then not be washed. Decisions, decisions....
Yes, batting can withstand washing. That is what is used in quilts. Batting or iron on pellon is good for in the hoop projects. You could try felt, but the colour might show through the fabric.If it is non washable, I probably wouldn't use it.