The k1 also has rtc and has official support for emulating many more consoles, the cpu is overclockable to 150mhz which gives it more grunt for the same.
Well, last I asked, the CPU being overclockable is currently a useless feature for emulators because of the firmware setting up the CPU for GBA compatibility. And as for "official support for emulating many more consoles", sure, but that's only because PocketNES, SMSAdvance, etc don't have any official support from Nintendo.
AFAIK, being a GBA clone it simply allows you to use the current GBA emulators. To actually do a decent job* of supporting the NES, GBC, etc would require a sort of super-GBA mode with more layers, a good bit more VRAM, and an ability to use higher than the 240x160 resolution of the GBA. I mean, most systems seem to use something like 256x224 as a base minimal and most PC emulators use 320x240 just because it's the closest to a standard resolution available on PCs (it's half 640x480 in both directions, and happens to be Mode X which was a quirky DOS-mode/VGA related thing).
Now, all of the above isn't to say that (a) K1 won't eventually get around to putting together a Super-GBA mode in their firmware (although from the sounds of it, they're not that interested and the whole 150MHz CPU has probably more to do with it being cheaper to source a 150MHz ARM CPU and downclock it than to try to order 16.67MHz ARM CPUs) or (b) for some adventureous hacker to disassemble K1's firmware and do it themselves (which isn't out of the question, but even then that implies potentially months or years before you'd ever see that Super-GBA mode). Really, given the K1 GBA lacks the X/Y buttons for SNES emulation and that'd likely be the big draw, as I see it--and the Dingoo is probably a better bet right now anyways given either way one is talking emulating--, I really just don't see that strand of logic holding out.
No, if anything I'd recommend the K1GBA for two reasons: being a hardware clone, it should have much battery life compared to all the other clones and seeing as how the market for old GBA hardware (especially flash carts) could easily dry up in the future, the K1GBA seems a safer long-term bet. But, then, that speaks more of what I'd be likely to buy in two or three years if my GBA broke. :/
*Please understand when I say "decent job" I mean in the context of "there is no real jarring effect when you go back to real hardware/another emulator that doesn't have the GBA's inherent limitations". PocketNES and Goomba Color are amazingly and I love them. Still, there's only a hand full of games that I really love PocketNES's squished graphics over other emulators--and that's when the hero sprite is too small. Of course, PocketNES is tons better for things like cheat finding, which is just good nature fun to do, than any other NES emulator I've used. And I still love Goomba Color's mixed SGB mode, although No$GMB is still the best for that. But, both would have been better with a higher resolution, more layers, and a faster CPU. So, a Super-GBA mode is attractive. It just doesn't sound like it's happening. Of course, I'd love to be proven wrong.