aggiegrad, you have it just the opposite, if you're a powerful rider, you will be spending your time in your largest chainring most of the time and therefore to obtain the best chainline for your biggest chainring, you'll want a shorter spindle length. If you're not as strong and will be spending significant time in your middle ring, you'll want the suggested or longer spindle. Either way, don't go too extreme unless you want to take your calipers out and test your math skills.

At Sheldon's suggestion, I use a 110 bottom bracket with my Sugino crankset because I tend to spend most of my time in my big 46 ring and by using this vs. the 113 suggested length, I can achieve a slightly better chainline for the majority of my prefered chainring/cogs.

Copied from Sheldon:

The spindle length mainly depends on what kind of crankset you'll be using, and doesn't have much to do with the frame. New cranks come with a spec sheet that lists what length spindle they are intended to be used with. Sometimes two lengths are listed. When this is the case, the longer size is for use on frames with fat seat tubes, because such frames put the front derailleur mechanism farther to the right than on a frame with a standard seat tube.