Several years ago, my son received some support from GPR, but after trying the stabilzer, returned to a Scott's without any support. The GPR just was not as good as the Scotts's. Also, a friend of mine who finished top 10 National Hare & Hound last year has used a GPR for about 9 months, and now the thing is leaking. Yup, he gets the repair for free, but has to send it off, and wait for it to return.
I purchased my first Scott's ion 1996, and it didn't need a main seal replacement until 2001. Cost me about $70 bucks. Wonder how much it would have cost in freight charges for the GPR over that same 5 years to get those "free" repairs.
Also, I raced a fast desert race yesterday, and at one point we were dumped into a really tight narrow 15 foot deep canyon for about 12 miles. After the first 1/2 mile, I turned the Scott's down one full turn, which allowed me to carve the canyon with ease. When the canyon opened up to a large highspeed wash, I took my clutch hand off the bars at 45 MPH (yup, with a Scott's that not even a problem), turned the knob back in one full turn, and resumed race speed. If you have a chance to ride with a GPR, you will notice that even on the lowest setting, there is still quite a lot of resistance, much more than is present when the Scott's is turned out 3 turns. I use the turning down and up strategy several time a year when the race changes from open to tight, and am thankful I have a Scott's each time.
While the GPR is a fine unit, it just does not compare to the Scott's unit when it comes to adjustability and durability. For my money, I'll buy the Scott's. As a note, early on, I kept a spare Scott's in the van "just in case". After a couple of years, I realized that "just in case" would never happen, and sold the scotts.
Rick