A Crash Course in Ergonomics
(I have one quarter's worth of post-graduate bioengineering. An ergonomicist I'm not. However, here's what I can share without making an ass of myself)
The closer to rest pose you can make a body, the longer that body can remain at rest pose. There are definite angles to have your display at, definite angles and heights to have your input console at, definite angles to have your seat back at in order to keep your blood from pooling, your nerves from being pinched, etc.
Another basic is that the less you move, the longer you will be comfortable.
CAD, gaming and fighter aircraft all have one thing in common - maximum visual input and minimal dextrous output. You'll note that when you design the cockpit of a fighter aircraft, everything is within reach. Control sticks on jets no longer even deflect - they use strain gages to get the full sweep of input from less than 1/16" of deflection.
I can't really speak to gaming (I have a Wii - granted, I've also got a 92" screen) but I can speak to hell about CAD. Maximum display has always been something CAD operators have been willing to pay for and a phat CAD rig will play the hell out of Crysis, if you catch my drift. Back when I was in the thick of it I ran three 22" displays when 22" displays were $1500 each. I used to have a Mitsubishi whatever-it-was that was a 27" CRT, costing a mere $8k. The point being, you have a giant visual sweep for your eyes to take in. Eyes, you see, move pretty easily (so long as they don't go more than 10 degrees above the horizon or more than 65 degrees below and stick to 30? degrees deflection on either side).
A tablet works because you aren't using it much and it's only 10" across. Once you get into touch screens over a foot, repetitive strain sets in pretty quickly - POP displays in restaurants usually use 15" displays because you can mash them and they're easy but even POP displays are going towards touch screens now (as evidenced by Apple's ubiquitous iTouch consoles). A 20" touch screen is murder - now, to execute a single command you're reaching your damn shoulder across space, using every muscle in your arm when you could simply be clicking your finger on the mouse.
'cuz that's the thing - the resolution of a mouse and the dexterity of an operator means you can cover 3 22" displays with one nice 12" mouse pad. In order to sweep across my entire field of view I only need to move my wrist about six inches, twice. And that's infinitely adjustable depending on how I want it. Give me a button or control under every finger and I'll rule the world - I've been using an MX Revolution since 2004 and a Mouseman Wheel from 1998 before that. And you can use it all day, every day, using no muscles below your elbow.
Lots of CAD operators use trackballs. They work pretty well, too. You have to move even less. In my opinion, however, they lack the precision. That's personal preference and others may disagree. Thing is though, even when you're getting into serious 3d command you're still talking about a mouse with function keys.
Look at it this way - a mouse is basically a pantograph. It converts small movements into big ones. So long as we're dealing with X/Y data on a flat surface, the best way to control it is through X/Y data on a flat surface.