Unfortunately, it kind of gets into a lot of grey, non RAW areas. I would say that from the elbow down (including, arguendo the joint) would be good for pistols or any kind of one handed work that didn't directly involve lifting a ton of weight, since most of the adjustments you make to shoot or swing are below the shoulder, and not having to account for muscle tremors or unsteady hands is going to make you much more accurate. I think that falls under RAI, though. As you said, a cyberhand is great for grip but not much else that's immediately obvious. Sure, you can hide a pile of stuff in it, and you can do amazing feats of dexterity (flipping a knife, dealing cards, playing the piano), but as written it doesn't do a whole lot else for you mechanically.
I'd half-agree with you. Adepts have a much longer upper end, since their PP just keeps growing with time. But adepts have a much harder time boosting their stats as a persistent effect, and they require karma that is at a premium during chargen. 'Ware just costs money, and if you trick a cybersammie out just right, you can come in with three or four stats at their full augmented bonus and be able to hot-swap your skills, as well as being fast as hell and twice as heavy.
Different styles of play, and you kind of have to munchkin that 'ware a little to get the most bang for your buck. You wanna see something dirty though, build a sammie with biocompatibility and adapsin, and transhuman prototype. Max out the starting cash, blow extra karma, and take indebt 15 and you should clock in around 600k. If you go all alphaware, you're looking at 7 essence worth of play with a 0.6 essence multiplier. I defy a starting adept to match anything that comes out of that setup.
