The original VPC-1 sounds very good but the potentiometer can become noisy after a few years (and they are no longer available).
VPC-3 uses a laser trimmed ALPS Blue Velvet potentiometer. Sound is almost identical but has better channel to channel tracking, and I've never seen a noisy one. Cosmetics on VPC-3 is also nicer as the knob is recessed into the front panel.