I've been rolling a Powertech alt lately and I've gone Cybertech. Which is pretty useful, Mako's pretty handy at Cybertech and Slicing, it lets you craft mods and armourings, which means you dont spend all your commendations on them. Plus those are useful for all possible characters, so you can easily mail them to your other alts.
Either Armstech or Armourmech carries the benefit that all your companions use tech weapons and armour, unlike Jedi characters who sometimes have a mix. Armstech might be the most useful if you plan to ever use your melee companions, as techblade/techstaff weapons are currently in short supply, so being able to craft your own is really handy.