I think most machines are easy to use (mechanically, the operator still has to have some skill). The 5XL is quiet – the only sound you hear is the stone on the lap. No vibration, unless you have an out of balance lap. Accurate – the digital head is accurate to within 0.03 degrees, and more important, repeatable within 0.02 degrees, according to the manufacturer’s specs. In practice, I find it repeatable to better than that over a short time span, as when comparing depth of cut on different facets.
I first bought a Mark 4 in (I think) 2004, because it was what I could (barely) afford. I upgraded to one of the first Gearloose-designed digital heads (don’t remember what year) and have been happy since. I’ve had the second machine for about a year.