>I would bet that the microSD's are cheaper and easier to get?
Most likely they are cheaper and easier to get than the other "memory stick micro" which I guess is a Sony proprietary format? I think they did the same thing with the memory stick pro duo format which I use in my Sony PSP with no problems, but it would be nicer being able to use a "universal" type of card. I'd definitely stick with the more universal microSD/microSDHC format.
>Also, the M-10 uses microSD, NOT microSDHC
Is there even such a thing as a microSDHC
I believe I have read the M-10 can use the microSDHC, most newer electronics that use the microSD can also use the HC version. Most of your larger microSD cards like 16GB and up will mostly be the HC versions, not that you can't find some that are not HC.
I don't have an M-10, but I do have quite a few of the microSD and microSDHC cards (Sandisk & Kingston) upto 8GB and have had no issues with any in the gadgets I use them in.