Really what it comes down to is preference and driving conditions.

If you drive on road or on smooth flat tracks with no big jumps and high traction cvd's are the way to go.

If your driving off road low traction in the ruff stuff and bashing plastic is the way to go.

My reasoning behind this is what causes most plastic drives to break is repetitive excessive torque such as punching the throttle coming out of a turn on a high traction surface which causes them to twist and then snap which mostly happens when you have a lota traction,power,tight slipper.
But they hold up much better to shock loads such as on throttle landings and large suspension travel where cvd's have a tendency to pop the cup or snap and the universal joint pins in this case the plastic has that bit of flex to absorb this.

The opposite applys to cvd's there great when there not subject to shock loads and do alot to reduce rotating mass and can withstand higher torque loads but un like plastic if something causes them to flex just a little bit there done for they also wear out faster and require alot more maintenance