Most arguments for transformers with taps above 15 include the benefits of longer runs. However, what about typical runs that aren't so long, but simply using the higher taps to keep wire gauge smaller? I ran some numbers, and it appears the extra cost of a multap transformer above 15 is pretty close to the wire savings on medium sized jobs (couple runs above 100, etc.). So for the sake of argument, let's say it all breaks even between trans and wire costs. Well, the labor saved would be significant, since pulling wire from a 12 gauge spool and placing it in the trench would be much easier than the 10 gauge. Seems to make sense, just pay attention to amp load capacity on the wire.