Just dropping by -- haven't been here a while. I'm generally in the "whatever works" school of thought, and the same holds true here. There are, and have been, some amazing guitar players who always wrap, and others who always barre. Far be it from me to say that Jimi Hendrix and Andres Segovia didn't know what they were doing, even though both played guitar completely differently.

However, there are some real issues of ergonomics at stake here. Ergonomically, the wrap is a limiting option; your freedom of movement when wrapping is severely constrained, unless you have huge hands like Hendrix did. A lot of folks who wrap have dramatically limited their technique in other ways (whether they know the reason or not), because they simply can't do much with the rest of their fingers when their whole hand is devoted to wrapping itself around the neck. There are exceptions to this, but for the most part the people I've seen who wrap either just strum chords (which may be why McGrath refers to a six-string chord as the proof that wrapping is necessary), or play fairly repetitive blues-based progressions. If that's all you're interested in doing, fine. But if you want to have more options, you may want to think about raising the neck and adjusting your hand position to bring your fretting hand in from underneath the neck, which inevitably means that you will dispense with the wrap in the process.

Moreover, those who advocate doing both may find that they are forced to hold the guitar in a compromise position that allows for both, but provides an optimal hand position for neither. Either that, or they are constantly shifting their posture to accommodate one approach or the other. It can be done, of course, but I don't think it's ideal.

The ergonomics of guitar playing are extremely important to continued progress; lots of people ignore them, and then get frustrated by their inability to play the way they would like to. I play in all musical styles myself, but I am fortunate to have started as a classical guitarist, studying within a discipline that places great emphasis on hand positions intended to allow maximum freedom of movement with minimum strain. And like Don Firth, as a confirmed "barre" player, I have never encountered a situation where I couldn't play what I wanted to play without wrapping.

With all that said, however, the original philosophy still applies -- the best way to play is whatever works best for you.