Interesting. Not too expensive either but I don't think I would want poly bushings in one arm and not the other. I'd like them to be the same.
"Mismatched" bushings are actually beneficial and is common in dual sport setups. For example, those in Arizona, Nevada, etc. that play with their trucks in the desert on the weekends but also drive them to work in the city will use poly in the lower arms and Delrin in the uppers. Rubber is too soft and doesn't last in the dunes. Poly is much stronger, but still flexes some. Delrin is very stiff. Since most of the feel of the terrain is transmitted through the lower arms, they use poly to help absorb and smooth it out. Since the upper arms are more for control, Delrin is ideal.
The same applies for the rear of our rigs. Except, we can dial it back a notch and have rubber in the lowers and poly in the uppers. All the arms locate, control and transmit vibes. But, the lowers will do most of the absorbing and the uppers do more of keeping the axle from rotating. For my street rig, I'm keeping with rubber-bushed lowers. I'll use poly for the adjustable uppers since I already have the bushings on hand and I don't wanna research universal rubber bushings for sizes, etc. I'm only making adjustable uppers since I'm lowered (and going lower) and will be lengthening the lowers when I make them to set back and center the axle. I'll fine-tune the pinion angle with the uppers. Yes, I could determine the pinion angle and make longer, non-adjustable uppers to lock it in place, but I want adjustability just in case.