PCAV or CAV usually averages faster times. The Plextor 712, for example, is faster at 12x PCAV than the Pioneer is at 16x ZCLV. The reason is the Pioneer doesn't change it's ZCLV from 12x to 16x until 4.1GB into the burn. So it basically is a 12x drive.
CAV-Constantant angular velocity--the motor stays the same speed througout the burn, so the data throughput increases as the circumferance increases.
PCAV-partial CAV--reaches the maximum using CAV and then runs at a constant CLV speed
ZCLV-zoned constant linear velocity. The throughput is constant in zones, then jumps to the next highest zone, i.e., 6x, 8x, 12x 16x.