The talk of MTB traction is certainly getting a little off topic, but I can't resist, as this is something I have put a fair bit of thought into myself.
Over the years, most of the "pro" tips I have seen concerning climbing traction support what kulivontot said. Basically, this can be summed up as "run a gear or 2 higher than normal when traction is bad, as the reduced torque will reduce the chance of breaking the tire loose". There is no denying that higher gears will lower peak torque, and this, in theory at least, will reduce your ability to break the tire free.
At the same time, wassertreter makes a very good point that if you do spin the tire, being in a higher gear will make it harder to recover and keep pedaling. If a higher gear manages to prevent the spin in the first place, then the point is somewhat moot, but higher gears, at best, reduce spins, so this is certainly worth considering.
wassertreter also makes a point about equivalent speed between two riders equaling equivalent force being transmitted through the tire contact patch, and this is certainly true when taken as an average.
The additional element that I think should be considered though, is that power is not delivered at a consistent average rate. it is delivered as a series of pulses, resulting from each pedal downstroke. A lower gear will result in a greater number of short duration pulses to get up a given hill, when compared to a higher gear, which will require fewer, and longer duration pulses.
This is where I think things get so puzzling, as individual rider technique comes into play. It is not so much the frequency and duration of pulses that would effect traction, as it is the peak force during each of those pulses. Specifically, minimizing the peaks, although if speed is to be maintained, that same power will need to be redistributed to other parts of the pedal stroke. So, in other words, the gear that allows you to deliver power most smoothly will be the one that delivers the most reliable traction, and that is where individual variation comes into play.
Rick mentioned an example above where "stomping" a big gear causes a loss of traction whereas "spinning" a low gear maintains traction. I would suggest that this is not purely an issue of gearing but of "stomping vs. spinning", and that some riders may find that a slightly higher gear actually smooths power delivers, vs. a low gear where instead of spinning they may in fact end up with a "choppy" pedal stroke, whereas others may find the reverse.
Additional factors are how body position is affected by gearing choice. Some riders might compromise upper body form more in order to push a bigger gear than others and, conversely, others may have trouble controlling their movements precisely at a high cadence. Also, it is worth considering the trail conditions. Everything above assumes consistently low traction, but some trails may be a series of slippery roots or bits of loose gravel, separated by areas of good traction. In those situations, the gear that best allows you to time your power pulses to hit the good traction will be best, regardless.
Without a peak torque analysis of a given rider, I think that it would be difficult to make individual prescriptions.