As I understand it, all EB volume pedals are passive, in that they have no active (battery-powered) circuitry. The "passive" pot is like 250k, and is designed for passive pickups, which are high-impedance out. The "active" pot is like 25k, and is for guitars with active pickups that can drive a lower resistance, as well as for expression pedal uses.
The pot value does not indicate smoothness. The lower the value, the lower the noise, so the 25k volume pedal will be a bit lower noise. But it will be terrible if you drive it with a guitar that has passive pickups, because it will load the pickups and lower the volume and kill the treble. It is also a problem to drive a 25k volume pedal with an FX loop out, because many amps have a pretty high output impedance on the FX send, as it is not buffered. Most Mesa amps have this problem. You are probably better off all around with a high resistance pot.
The TAPER controls the smoothness of the pedal sweep. A linear taper will be not sound very smooth. An audio, or logarithmic, taper will sound smoother. This is because we hear relative volume as a logarithm, as in dB.