I had XRVs on my Suncruiser for the 18 months I had it. When I got my '04 Bus it came with XZE tires and I put 30K on them in 3 years and they were great. The '07 Bus has XZA3 tires, which are similar to the XZE.
The biggest differnce is that the XRV was designed for RV's, not trucks. Michelin tried to make a tire that would ride better and the XRV was the result. They accomplished this by using a thinner sidewall that would flex more than the heavy duty sidewalls found on truck tires. Their reasoning was that RVs don't carry as much weight as trucks and can get by with a thinner sidewall.
That's a nice idea but it had drawbacks. For one thing, you need to be right on top of your air pressures and weight readings. If you ran them without the required air pressure for your axle weights the sidewalls would fail and blow out. Also, you didn't want to get too close to curbs because a brush against them could cause a ply separation in the sidewall. These were the tires that developed a reputation for those dreaded "zipper tears" that were always denied warranty coverage.
The XZEs on my '04 Bus were great. I really didn't notice any difference in ride (although it was a heavier RV so that makes a difference also) and they held up great.
I'd defintely recommend the XZE over the XRV any day.