I've got both. I figured the VMP5 would just need American electronics to be as good as the P5, but it sounds so good, I never put them in.
The American P5 gets deeper and darker, the VMP5 has more growl (both have maple necks). The P5 sounds more polite, the VMP5 sounds more aggressive, both are great basses. For $299, the VMP5 is a no brainer.
The only real advantage is the P5 stays in tune better between practice, a minor issue really cuz I always hook them up to a tuner before I play.
P5, 5/1, SKB 3005, VM P5, CS '59 NOS P, Fender JPJ, Antigua P
CMD 102P + 102HF, LMII + Thunderchild 115 Composite
X2, TU2, Fodera 2000, Bassbone, Compressore, Fdeck, Pedaltrain