Drakah UI on both (Matter of taste I guess).
Ranger is, and has always been, my main. Shammy is my bot, levelled up for the purpose of helping out (though he is great fun to play also, and I really love this class I must say!). Shammy has to be the best support class for 2 boxing any melee really.
Shammy on "off-hand" PC, heavily decked out in shortcut keys with remapping and really heavy use of Voice Triggers (I use Tango!'s excellent engine for that). I never rely on macro's - impossible to interrupt etc. and I prefer to play both toons "actively" though I rarely look at shammy screen, I always knows what he is up to.
For the fun of it, I've experimented the other way around also; using shammy as main and ranger on offhand, but I guess since I am ranger by heart, I find it hard to leave him alone and not constantly try to optimize what he is doing.
I guess what it comes down to, is your personal playstyle and preference. I'd say, play the one you enjoy the most as main, and use the other to help yourself out doing just that - enjoy yourself
