I have the older Harbor freight lift and a Larkin lift I use the Harbor freight and the other one sits in the shed. Not to say that the Harbor freight is that great, it works and the foot lowering hydraulic release is a little jerky. The aluminum one you show looks like it nicer, longer and wider, so I'm assuming more stable. It looks like it might be a twist the handle for releasing hydraulics, this is probably a little easier to control downward motion as you have more control with your hands as apposed to the foot control.
I watched the F&S video's and read some reviews, it seems very impressive. One thing I'd say is that the Harley may be perfectly balanced and the frame exposed enough to center the lift at that balancing point. The F&S lift looks like similar designed with box tubing to the steel Harbor Freight, but I assume they have tighter tolerances, heavier wall tubing and maybe use bushing instead of just holes in the square tubing. But back to my Eluder, I cannot find a perfectly centered balance point on the frame for lifting. I think I moved the jack as far back on the bike and was very close to balance point, but I had to block the rear wheel as it wanted to sit on the ground (I just lift to the jacks first locking detent) for oil change. So my point is the stability is partly the jack quality and width of jacking points, but it also depends on where you can lift the bike from and it's center of gravity. It would be nice to hear from someone that already owns a Venture or Eluder and uses the J&S jack. Myself being so cheap, and not one to use a motorcycle jack that often, I don't know if it's worth the extra $400 for the F&S to me. If you have multiple bikes that you use a lift on more frequently, definitely worth the money. That's kind of how I decide to spend a lot on name brand tools, versus something that I barely use once in a while, than I'll buy Harbor Freight stuff.