? I cant see a ton of advantages. I can do most of the hammer ons that are used within a chord, just using a normal fingering for a barre chord, its just a little harder
i play the g-chord using my thumb on the on the low-e, also dave mustaine uses his thumb on the high strings to be able to stretch as far as one octave on one string
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o, i just meant like as far as barre chords go. Mostly for playing Blues and Funk
The main difference I find is the 'colour' of the chord sound. Play a normal barre chord G. Then play a barre chord G with the thumb for the bass E, whilst muting the A string. With the thumb muting the 5th string the G chord becomes brighter in sound.

Personally for me, it made sense to use the thumb when learning some songs e.g. Enter Sandman. Wasn't til later that I discovered Jimi did the same thing.
I use my thumb all the time. If I feel like it's better to use it on that certain chord then I will. Only problem is that it kills the thumb after a while!
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I have one or two songs where I add in my thumb on the low e string. So I guess if it helps or makes the song sound better I say Why not use your thumbs!
I never use my thumb, the only time ive ever used it is when playing 'Cant stop' By red hot chili peppers

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