Insite Heathen.
I haven't tried the MDT, I'm sure it's effective. There's really not a lot to a muzzle brake, it's all about venting gas in a direction that opposes the bore.
One potential downside to the MDT is how the ports of the brake are positioned. Much like the Area 419 and APA muzzle brakes, the ports are directed back at the shooter. Great for mitigating recoil, bad news for the shooter. These types of directional brakes do send blast/concussion back to the shooter, so that's something to keep in mind.
The Heathens first port, which acts as a the main port, is perpendicular to the barrel/bore. This means that gas is vented out to the side, rather then being directed back to the shooter. This does make a difference behind the gun, especially during comps or long days behind the rifle. All the concussive blasts add up, and can be pretty fatiguing. The Heathen does a good job mitigating that blast, better then the Area 419 and APA brakes that I've had. But there's still some concussion, and that just comes with the nature of the beast of having a muzzle brake.
I also find the Heathen to be a bit more refined in design and manufactured quality then the Area 419 and APA brakes. Myself and others I know have had issues with the Area 419 collar locking up, the threads on the locking collar are really fine, and in my experience don't seem to handle carbon or other fine debris well. The gills of the brake are also not radiused on the Area 419, and will slice your hand up good in the event the locking collar gets stuck, and you try to fix it by hand (ask me how I know).
I've never tried the MDT brake, though I'm sure it's effective. It's certainly not a bad price, but just keep in mind the port angles and how that may effect you if you do decide to go that route.