I threw both of these on a 40' challenge shot while attending Storm U a few weeks ago. With identical drills the VR Pearl went longer before it made it's move. The MP was earlier and stronger overall, I thought it was a more rolly ball compared to the VR Pearl. For me the MP allowed me to open up the lane more.
Reaction wise the VR Pearl reminded me of a smoother Reign that didn't squirt on the oil. MP is more like a Agent, Gravity Shift combination - which a lot of other people have said and I agree. Overall I would say the MP is stronger and some of that is probably because it does roll earlier than the VR Pearl but it also has a stronger coverstock on it. Depending on the bowler but I'd say the MP is 3-5 boards stronger overall.
I don't think you could go wrong with either ball on a THS. I'd choose based on the reaction shape you want. If you want longer and a strong backend go VR Pearl. If you still want strong but earlier roll and more control go with the MP. If your THS does have a lot of friction I do think the VR Peral would probably be better due to the extra length it gets. If you bowl tournaments or sport shots I think the MP would be more versatile. I got a MP drilled up after returning from Storm U and it's been my workhorse ball this season. I feel confident throwing it on med-light to med-heavy conditions, THS or sport shots.