Well GMPP specs are listed for both front and rear, he must want to know what's better, dorman rear or GMPP rear.
The GMPP is bigger than the stock one. It is also hollow. It's a good replacement for the stock bar. The dorman is a stock replacement. I see you are in california, so you don't have to worry about the harsh weather conditions that those on the east coast or midwest go through, which can deterioate a hollow bar. The BMR's are also nice. They actually stopped selling them on their site. They are thick bars and are good quality just like their trailing arms. It depends on what you want to do with the car. I have been happy with the GMPP handling kit on my car which is a daily driver since the kit first came out many years ago.
What I'm trying to do is get the suspension set up for auto-x and the canyons. I know what I want I'm just trying to find out and see all of my choices. For instance I found this SLP sway bar package which comes with the front and rear but I'm might just use the rear only.
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I have the addco myself and it made a huge improvement, live in cali as well, Get BMR if you want it for a lot of twist and turns, if not ADDCO and some BMR trailing arms or GMPP, You can get the Strut Braces but honestly didn't feel much of a difference and I have the BMR front and rear, I would go Sway bars before Strut Bars any day.
Also don't forget that UMI offers trailing arms as well. They are just as good. Aso as a heads up, the BMR's are very thick. If you are running a high offset and wider wheel they have the potential to rub the trailing arms.
Back to the sway bars. I can not tell you how the GMPP set up is for autocross. I have never autocrossed. They may be enough for what you need them to do. The bars are hollow.