I still vote CFFA3000 for best USB/Flash solution for the Apple II simply because of the ongoing support. These boards have been supported since they came out years ago, including the earlier models. So that's my preference. But there are other solutions available like BMOW Floppy Emu and some other card (I forget exactly) that is an MP3 player that fits inside a standard expansion slot.
Vague rumor has it there will possibly be a redesign of the CFFA board in a couple of years. Thus likely keeping it at the top of the heap. And I hope it supports standard/micro SD cards as I feel CF has become a niche format for pro photography. Not many consumer products are using it these days.
It would also be nice to see an R&D card that's compatible for the //c. The //c has been gaining popularity for many reasons. Mainly small size and having basic interfaces already built in.
So what's the future of flash memory for Apple 8-bits? What can we expect to see?