i have found my lowrider is just as accurate as my mpcnc once dialed in, but it was a little bit trickier to get it dialed in cause there is more little things to adjust, especially on the Z axis.
Both my machines run to 0.1mm and i can often get it to 0.05 if i am careful on small things (less then 150mm square)
the main downside to the lowrider is the max speed / acceleration tends to be less because the gantry setup is heaver then the MPCNC, so it has more mass to throw around.
i run 2000mm/sec acceleration on my MPCNC, my lowrider is closer to 500mm/sec to avoid shaking.
the acceleration of the MPCNC makes it a bit more flexible for laser
one advantage of the lowrider is you can park the gantry at once end of the bench when not in use and use it as a work bench (the gantry only eats about 300mm of desk space)
The lowrider can be made MUCH bigger then an MPCNC
the MPCNC caps out at about 400x400mm if you want to be doing metals with it, little bit bigger for timber although not much.
The main problem is that the side tubes start to flex a bit which reduces your accuracy.
the lowrider caps out at 1.2m on the X and the Y has no real technical limit. (its more what will fit in your shop)
Final note is Z axis
the MPCNC is top down, so the longer the Z the more flex you get at the bottom of travel (which is when you want it really tight) so it limits you a bit in your Z axis (mine is about 90mm to do aluminum on it)
the lowrider works from the bottom up, so you get the most flex at the TOP of your travel.
So having a really long Z axis does not matter so much when your milling down low, the rest of it just hangs there. (my lowrider has a 260mm Z, i use about 50mm of that on average, but its nice to have )
hope that helps in the decision process, both are great machines, but require a bit of TLC to get dialed in really tight.