I would guess the Quark is easier to program from what I have heard. The choice would be yours really. I think the MGM may give you more options in battery selections down the road if needs be.
"if you've got something to say, say it peacefully"
I have both.... I really cant decide which is better. I really like them both for different reasons and hate them both for different reasons.
MGM
Upside:
Runs stone cold. I havent thermalled it yet.
PC programmable if you get the newer ones from Mike, so easier to program.
Downside:
Has a bit of a touchy LVC and you need to use high quality lipos to not have premature LVC problems (I personally see issues with 20c, but not with 25c enerland packs)
They still have a little bit of a funky brake, but only a low speeds and it can be completely eliminated if you run forward only.
Quark
Upside:
Still the smoothest throttle with the least cogging around IMO. Very stable predictable brakes.
Runs ANY brushless motor. I haven't been able to find a motor it wont run. Outrunner, 2 pole, 4 pole, 6 pole... anything.
Downside:
Tends to run hot and at minimum a good heatsink is needed on the back of the case. Worst case is you need to do the "heat mod" to it.
No PC programing, but its still pretty easy so not that big of a deal IMO.
Some have cogging issues on 6s. Not a problem if you are planning to run 4 or 5s setup.
I can't decide if its more fun
to make it...
or break it...