The stabiliser is mostly for the 3.5oz cartridge, however if you add that to the JetBoil you need to add that to the pocket Rocket too, same "problem".
By that I mean if you find that one is unstable so is the other....
As for the cup, some use it some don't , it isn't necessary.
As mentioned I don't really have a horse in this race because I don't use my(different...) JetBoil and have plenty of stoves that I don't need to justify having, I am just pointing out some figures.
BTW with the Jetboil I would say that the key feature is the one mentioned by the Oregon Mouse, and that is "convenience" although at least initially many liked the efficiency that is a fast boil with very little fuel usage.
Some of course base their system purely or mostly on weight , others have different priorities and that is why you will never see a single product that will be best for everybody.