Sumiko MMT vs FT-3 vs FT-4 opinions

I recently acquired a HW-19 MKII with a MMT mounted. I've found at cartridgedb that the FT-3 and FT-4 have the same mounting distance. I'm looking at them for a possibly easy, non destructive upgrade. I've read the FT-4 had an on the fly VTA adjustment, but other than arm type they all seem to have the same structure. Has anyone AB'd these arms anytime in the past? Should I just leave well enough alone for my $200-$300 cartridge budget?
As I recall the FT's are supposed to be a better arm (actually there are a lot that may be better), but isn't there a difference in mass as well as arm shape? I have the MMT and I wouldn't upgrade it just to try to squeeze the last iota of performance out of an inexpensive cartridge. Mine works fine with a Benz Glider - I have no angst whatsoever. If I were going to up-grade it would be the entire system.

Leave well enuf alone. :-)
Cartridgedb has the FT-3 at 14g but no mass info on the MMT. I've read the MMT is also about that, so I guess between the MMT and FT-3 it's really the arm shape and the more expensive FT-4 providing on the fly VTA. I'd love the convenience of that but I might spend my listening time endlessly tweaking VTA.