OT: Flash Memory Recommendations?

I just purchased a cheap-ass digital camera which takes
either "SD" or "MMC" flash memory in 16MB, 32MB,
64MB, or 128MB sizes. Quick research reveals that
there are (at least) half a dozen different types of flash
memory ... and I assume this is just a replay of the old
VHS vs. Beta (or "DVD+" vs. "DVD-") competition,
i.e. a strategy to lock-in consumers. I have two questions:

1.) Of the two flavors that my camera accepts, SD or MMC,
are there compelling reasons for purchasing either one?
Has either one established a clear market lead? What about
technical advantages?

2.) Is there a good local source for this stuff and what might
one expect to pay for it?

Thanks in advance.

Fritz