ZillaJoe...overall your best bet is just that, and you'll find most guys running an LT with that exact combo.
For MX, a little smaller is better from what I've heard, on trails and mud there's no substitute for aired down big tires for all-around performance and clearance.
You can use the 21F/20R as a middle ground, or buy two sets tailored for the two different riding styles (smaller for MX, larger for trail/mud).
There's a lot of advantages to bigger tires, but one disadvantage is weight and rolling resistance of a heavy tire aired way down.
That's why you generally see smaller tires on MX tracks, because they're trying to get every ounce of performance for that particular terrain.
Flat trackers and pavement use even smaller tires than MX, I'm not even going to guess why but they look a bit silly to me.
You don't have a lot of options for narrow fronts unless you go with drag style tires.
I've noticed that narrower fronts reduce steering effectiveness as well as making it less stable at higher speeds (off road, not on pavement).
The only place a skinny front tire helps with steering is in the dunes, where it'll sink into the sand...but flotation suffers due to higher pressures needed and a smaller footprint.
Size consideration aside, a very important aspect is which brand and style of tire you buy.
Some tires that are otherwise identical handle completely different (traction, sidewall stiffness, puncture resistance, etc.).
Can't really tell you a whole lot about which tire would best suit you, as all of my experience is with desert riding (baja/sand/rocky trails) and I haven't looked into any tires other than that aspect.
Running 22x11x10 itp HOLESHOT xct'S ON REAR AND MAXIS RAZER ll ON FRONT SIXE 23X7X10..GIVES ME A LITTLE MORE GROUND CLERANCE AND COOSH IN THE TUSCH.
Post a pic of that quad, I'd like to see it!