The BKs only work with 2 pole motors, so won't work with Neu motors should you decide to upgrade later. Also, the programming is VERY limited and there is no LVC for lipos, so you'd need an external one. Warranty work could take ages if something goes wrong.
The Quark works well, but does tend to heat up. The "internal heatspreader mod" fixes this, but opening up an expensive ESC is not something many want to do. Programming is OK, but can't use a PC. Has a built-in LVC, but max cutoff is 3.0v/cell - some people would like to set a 3.1v or 3.2v/cell cutoff. It says it will do 6s, but no one that I know of has gotten it to do that. 5s is really the limit. That said, it is a very smooth controller and works with inrunners, outrunners, and slotted rotor motors (like the Neu). Customer service is good and fast should something happen.
The MGM runs very cool and can run pretty much anything. The new ones have a built-in switching BEC, so that is one less thing to buy. An LVC is also built in. You can program it with a PC, but not sure it'll be as good as the MM in that regard. There is an issue with reverse and brakes, but only happens at very low speed. Warranty work can take a while.
I think that basically sums it up.
