High pass sharpening is actually the same technique as Unsharp Mask sharpening...it's just a different way to go about it, and with a little more flexibility.
Sharpening is one of those things that few people fully understand (myself included). There are a few books on the subject, one that I've been meaning to read is called 'The Art of Sharpening' (or something like that).
You could also Google yourself several days worth of reading on it.
In a nutshell, I don't think there are any hard rules when it comes to sharpening (or photography in general, really). Sharpening is usually done to taste, so everyone is different. And different photos will respond better to different methods or strengths of sharpening.
High pass sharpening builds more overall contrast than unsharp masking.
High pass sharpening sharpens less overall.
High pass sharpening is a smidge less noisy than unsharp masking.
The problem with high pass sharpening is loss of precision. With the sharpening that takes place you are also getting a contrast increase. Two variables change together. As you get the sharpening you want are you also getting a desirable contrast change at the rate you want? You can't control the two separately and that's bad.
A better technique, is to switch to L.A.B. mode. Duplicate your layer, go into the channels tab and deselect everything except the Luminosity channel ( the pic becomes black and white ) now apply unsharp mask to only this channel. Click back on all channels and go back to the normal layers tab. Now you can adjust the opacity if you need to fine tune slightly. This will sharpen the lightness info without effecting any of the color info.
Highpass can be quick done in RGB mode though so sometimes its quicker and more convenient to use that.