I have been riding both harnesses, the MX for 6months, and the Ride engine 2017 for a year.
The Ride engine feels nice and tight with great back cushioning. The mystic is slightly looser, thinner back cushioning, but somehow feels lighter and more comfortable after a long session. Both feel nice and locked to the body. The MX is just a bit larger for a said size (I am 65kilo/175cm perfect using the S). Both have a great low profile shape. The MX seems to "wrap around" the body better. The RE is lighter on the spreader bar but the harness is heavier than the MX.
I now always go for the Mystic. Heres why:
-The MX is adjustable on both sides of the spreader bar. Rock solid quality straps. The tips are stitched. A lot thicker and wider than the RE`s flimsy, and always getting loose straps.
-Due to being beefier, the MX spreader doesnt move around as much as the RE which turns and twists around.
-THE ROPE! The MX rope is just a bit thicker and doesnt elongate like the RE. After a week of riding the RE the rope got 3~4cm longer. None of that with the MX. The MX's rope is a lot easier to change being in front of the harness. It is so hard to get the RE rope nice and tight. And the metals wholes the rope goes through gets rusty.
-Zero problem with the MX spreader clicker. In hard crashes I have had the RE spreader tubing get unhooked from the spreader bar.
Notes:
-Both harnesses are S SIZE.
-There is no side leash connector/ring on the MX. But very easy to add a strapped/ring to either side around the straps. The RE as one ring of both sides of the harness BUT. a friend of mine had them ripped out getting pulled hard during a missed trick. I haven't had any problems with mine though I don't use the harness for unhooked tricks.
-Both are hard back but MX is very very slightly flexier.
-From the pictures I had just re-tighten the rope on the RE...still started to elongate again.
-I do not use metal rings but sailing low friction rope glide rings.
-The mystic comes with a pouch which includes quite a long spare rope. Also has a knife built into the spreader bar.
So basically having a mystic spreader bar/rope with and adjustibilliy mixed with the RE harness would be the perfect harness...Though I give a slight edge to the mystic on long sessions for comfort. Personally I also like having a looser but stiff harness? If that makes any sense...
My score:
2017 RE 7/10
MX 8.5/10
Mystic really did a great job there. Solid harness. But pricy.