Tahitian I believe you have already answered your own question.
Other than suspension and brakes you prefer the YZ.
Take a page out of Roger Grangers book with his 171lb TM400,
Shave as much weight off the YZ as you want to spend,
Brakes on an Aberg are no better than the YZ, but they can be dialed in much better than standard or instal a Bigger XT500 front wheel,
Both ends of your VMX Suspension can be dragged into the 21st Century it's just going to cost you!
As good as TT500 Abergs are, I believe the SUZUKI SP/DR 370/400 based bike is substantially better in every way!
To me it is one of the rarest and most desirable VMXers ever made,
And you can build one or a reasonable facsimile of one for much less than the TT.