I've been playing Mike's basses for years and love the feel and tone. When he released the UVP4 I immediately went to his shop to check one out. I have always loved vintage radius basses and figured I'd want to order one. I went back and forth playing a P4 and a UVP4 at his shop and ended up liking the P4 with the 12" radius much more. Just my experience, but I think his stock P4 and V4 necks are the most comfortable and easiest to play of any bass I've ever had.
Besides, that's what Mike himself plays - a P4 with alder body in Aztec Gold, P width neck with 12" radius brazilian rosewood board.
I spoke with Mike a bit on Friday. I'm leaning towards the P4. If I end up ordering it, the only change I might make is to request the smaller, vintage frets. But I'm sure even his standard frets would be fine.