An arm to live with for years to come

I need some help from my fanatics and neurotics :-)
I am trying to fully "trick-out" my VPI HW 19 Mk IV
and now have only my tone arm to upgrade. I am torn between
the JMW 9 and 10 and SME IV and V. I just want to get the rig to the point where I can fully concentrate on software--help me I am almost there!

I have the following:
MK IV with latest Aries bearing and platter & Tip-toes
SAMA on black diamond racing cones
Grado Statement Series Reference
Steel Delrin clamp
John Boo's 2.5" Maple cutting board
AQ PT-9+ (anaconda)
I've owned that same turntable and tried several arms, but not the ones your considering. Based on my experience with that table and listening to tonearms in many other situations, I would go with the SME IV or V (of the ones you list).

If you want a unipivot design like the JMW, you should consider the Graham. Preferably a Tungsten series, as late a model as funds will permit.

If the Walker motor controller works on that model VPI, it would improve performance as much as your tonearm choice. I was stunned at how much the Walker improved the TNT, even over the VPI controller offered as original equipment.
I am guessing that you want the liquid midrange that the unipivots can give, and the solid bass response and detail of the SME gimbal-bearing type arms. Usually you have to give up one to get the other. Except if you get an OL arm like the Silver, Encounter, or Illustrious. They are known to give liquid mids like the best unipivots, and the deep bass and detail of the best gimbal-bearing arms. They also have great musicality and are not analytical sounding. I would strongly recommend considering them, as I think they will do better than either of the arms you listed, and cost less too.
like albert, i've owned and used this tt, too. maybe a decade ago, or more. best combination i tried was the (long-out-of-producttion) grado arm with the highest-end grado cartridge then available. weird lookin' but on the path towards nirvana.

i would avoid the SME arms (which i've also owned), because of thier bloated bass. but, as always, YMMV.

The SMEV is not an ideal match for your table. The bass is not accurate or wasnt in my set up. I switched to a Graham with very good results. The Naim aro would also work well, much better than its plain construction would suggest and that would be my choice.
I'd go with the JMW 10 or 10.5 but with the caveat that they don't handle edge warps with much grace, at least with the Grados (I have a Reference too, the original version).Then I'd ditch the clamp in favor of a Ringmat. This ridiculous-looking thing (which isn't supposed to work well with VPI TTs) really did wonders for my early model TNT. At least see if you can borrow one and try it.

The Walker unit undoubtedly bests the earlier model VPI motor controllers, but I would question whether it beats the SDS, which is the best favor I ever did for my TNT.