Cmk, that question has been asked here, on AudioCircle, and on Audioasylum. To my knowledge, no user has ever directly compared the two. I mentioned the Rega mod to Kevin at KAB, and he explained why he would not recommend replacing the Technics tonearm. Of course, he's in the business of optimizing Technics tonearms, so it's in his interest to convince users of his method. Nevertheless, I believe he endorses what he thinks are truly the best options for the Technics.
On the other hand, people who have done the Rega mod (but have only compared to a stock Technics table) love the results.
Personally, I would only do the Rega mod to a used Technics table and with a used Rega arm. I'd hate to spend the money buying new, and then tear apart the table only to discover the results were not up to my expectations. Doing the mod with used gear lessens the risk, IMO.