Brian,
I have been using the Harmony M for several months and it does a great job. It does, however, have some quirks such as a slight delay when you change chords.
I only had a few minutes with the Harmony G at a local music store. It was pretty slick, but it too has that same, annoying delay, but not as pronounced as the Harmony M.
If I were still sitting on a stool playing my 12-string Yamaha and singing, the Harmony G would definitely be in my bag of tricks. You can set it up in seconds, it provides a very crisp, clear, realistic harmony, excellent vocal processing and it's quite small.
I'm not sure if you can use the Voice Live 2 with two instruments at the same time, which may be a problem if you use both guitar and keyboard at the same time. You may want to look into this in greater detail before buying.
Good Luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)