I have a Scotts
on my YZ426 and a WER on my WR250F. I race MX and HS with the YZ. I don't notice that much difference on the MX course without it. I know this because sunday the pin that fits in the tower worked its plastic collar loose and slipped down into the tower, which disabled the linkage. I don't know how long I was riding on the MX track with it disabled but I never got headshake on the YZ. When I HS the YZ, there are some long fast bumpy straights that it helps on. If it saves me from crashing once, its worth it. I also think you don't have to grip the bars as hard, which really helps me in the 2 1/2 hour HS races. The scotts is easily interchanged between bikes (just buy a mount kit for each bike). The Scotts tower is a very clean mount on the YZ/WR, no drilling required. The whole package with mounts and tclamp is nice, but expensive unless you were going to buy new tclamps anyway (I did, my wingspan is 6'3"). The scotts fits under the crossbar of Renthal
CR highs, but it is tight. With protapers it is tough to mount a pad. You can also adjust the Scotts on the fly.
I run enduros with the WR. The WER works just as well, and helps out alot in rocks and roots. I like the WER because it is not in the path of placing a crossbar pad. You do have to butcher your front number plate, but I put a DHH headlight on my WR and no butchering was required. I am way too busy riding to adjust my scotts, so for me adjusting while riding is not a big deal. The WER is not as easy to mount as the scotts. Drilling or welding is required, along with the headlight/number plate cutting.
Summary: If you want to save a few bucks, really want your crossbar pad, dont mind butchering your number plate or headlight and drilling or welding your frame, go for the WER. If you have multiple bikes, buy new tclamps/mounts anyway, and feel you need to adjust on the fly, go for the Scotts.