I've been running the Acerbis rally guards on my KDX's for about 5 years now. i used to run the alluminum guards on my YZ, but a few of the guys at the HS and GNCC's that I race told me stories of breaking hands and wrists after hitting trees at speed (they said that the Al alloy on the Acerbis Rally-Pro was to rigid, upon impact their metacarpals folded around the bar), they suggested the all-plastic rally's. My parts guy (KTM racer) told me the same story, and my neighbor (2nd place 1985 Blackwater 100, 250 4-stroke) told me stories of the bark-busters folding back and breaking wrists during impacts. I think that there has been a dramatic improvement in handguard tecnology since 1985, but I hit ALOT of trees and the plastic rally's have never let me down. I still have the same levers and perches that were on the day I put the guards on. If you ride year-round in an area that gets all 4 seasons, you will want the spoilers (they keep alot of mud off the grips, and help keep the wind off in sub-0 temps) and I have had to replace those a few times. I never had any trouble with the bars bending (AND I CRASH HARD), but I use rubber mounts, which have a little give. One of my KTM riding buddies had the Al guards, went down hard, and the bars simply bent between the mounting bracket of the bars and the inside mounting bracket of the guard. I think that the Al alloy guards look better (especially the Cycra's), I guess it just depends on how often and how hard you hit trees.
Best of luck, never stop riding!!!
-Nick