Here is what I just posted on the other current spoke choice thread. IMO it is what choosing spoke gauge is all about:

The correct choice of spokes is very simple. Spokes do not routinely break in the center, only at the J bend and near the threads. There is plenty of tensile strength in even 1.5 mm spoke sections to accommodate very heavy riders. Even the lightest SS spokes available these days have the same gauge J bends and thread areas as the heaviest, so have the same inherent resistance to breakage at those points. There is no strength-based rationale for using any spoke heavier than 2.0/1.5/2.0. Because the lighter spoke stretches more at any tension than a heavier spoke, it has more "return travel" before going slack when the rim is rhythmically compressed at every point on every revolution routinely and compressed by accidental stresses like hitting a pothole occasionally. That helps to keep the spoke from fatiguing and failing at the previously mentioned spots, the J bend and just below the threads. For the vast majority of riders the most durable and most comfortable wheels they can possibly ride will be built only with such spokes like Revoutions, Lasers, and CX-Rays.

The one reason to use heavier spokes than that is to obtain greater stiffness, which according to Rob at Psimet is not best accomplished in that way. The lighter spokes do result in some loss in wheel stiffness. Some of this lost stiffness can be regained by using more spokes rather than fewer, but probably not the entire amount. If stiffness is an issue for you that can't be resolved by more spokes and a stiffer rim, then perhaps a heavier spoke is proper for you. And in that case using the heavier spoke first only on the DS and maybe the front would be the smart plan. It is imperative to preserve the high level of stretch in the less tensioned, NDS spokes. Using heavier spokes on the NDS should be avoided if at all possible.

To give you some idea of the quantities of stretch we are talking about, a 2.0 mm diameter spoke stretches ~1.0 mm at 120 kgF, the common DS tension or 0.5 mm at 60 kgF a common NDS tension. That NDS stretch is not sufficient to protect the spoke from going slack periodically when the wheel is in use. The greatest popularity of 2.0 mm spokes was back in the day when wheels were not so heavily dished and DS and NDS tensions were commonly much closer. So the NDS stretch was closer to the 1.0 mm on the DS. That is not the case now. Revolution spokes however stretch about twice as much, so even at 60 kgF on the NDS they are stretched about 1.0 mm, plenty to protect against most instances of rim compression which could cause slackening of the spokes.

This is it in a nutshell: lightest spokes = best wheels unless desired stiffness cannot be achieved by spoke count and rim properties. If the DS and front wheel stretch is too high and the nipples bottom out before full tension is achieved, just go to a slightly shorter spoke. Don't change to a heavier spoke to moderate the stretching.