I have owned the G bass before, but not the GV (because I don't do 5'ers). I own neck thru Cirrus and a bolt on Cirrus. The bolt on feels WAY better than the Gbass. Definitely the most comfortable bolt on I own, next to my Foundation S. The bolt on Cirrus is 24 fret 34" scale, the G bass is 21 frets, if memory serves, just like the Millennium. The bolt on 5'er is 35" scale.
That's good to hear that the neck ergo's is in the same ballpark as a Millennium. I could definitely go for another four-string in the arsenal, as most of my basses are fivers.