J-heads are tried and tested, just like Ubis hot ends. I've had excellent results with both.
The nozzle size is harder to change on the J-head vs Ubis, but I think the J-head design potentially can have a sharper heat break (a good thing) due to the greater potential for active cooling. My Printrbot Ubis has jammed twice when I left the hotend on without active cooling, but if you only enable the heater when the print is ready, you shouldn't have any problems there.
For me though, the big advantage of the J-head is the range and diversity of mounts for these that will match Simpson because of the Kossel-compatible flange, from things like goopyplastics's c-clip (
http://www.thingiverse.com/thing:107890) to Johann's Kossel fan shroud (
https://github.com/jcrocholl/kossel/blo ... nd_fan.stl) to Glenn Beer's fan mount (
http://www.thingiverse.com/thing:335047).
FWIW, SpiderPig's prints were all with a J-head with 0.35 nozzle, using Johann's fan shroud.
Also, regarding stepper torque, I would go with as high torque as you can find. There's enough friction in the system that a little extra torque would come in handy. My Kysans were near the edge of the passive cooling limit (~1A stepper driving setting) and at the most-extended position would sometimes slip. Ultimachine's web site has the torque specs for these.