I ride with a 660 grizzly for a few years now and its plastic skid plates hold up well. Infact the plastic plates slide over logs and rocks more easily I would think.

Here is a 450 KQ winning a 500 Utility shootout.

 

The Plastic Skid Plates are really durable. I was at the dealer and they were showing me how it works. The guy pretty much bent the thing in half and it just popped back straight.

 

the plastic skids may be durable but if it can be bent in half how much protection do you think your getting

 

Because the skids can bend may put heavy pressure on the drivetrain. The question is, how much pressure can an axle or gearbox take. Does anyone, want to take that risk? Also, a solid skid plate ties the frame together more, giving it added strength and durability. A few days ago, while out riding, I high centered 3 times going over downed trees. Glad I didn't have plastic. Don't know what would have happened had those trees been big rocks and bolders.