Apologies but which unique performance characteristics do you mean? PU is far superior to PVC coating in nearly every way except cost. PVC on a nylon is almost redundant for the cost of nylon why not just go with a PU? I assume since you are using a 3x PU you are looking for the durability of Poly with a 100% PVC laminate.
Do you have the option of upping the weave rather than the PU coating? For example: You use a 600x600D Polyester with a 3x PU coating. Just upping the waft to a 800x600D you should be able to get the same results as doubling the coating for few cents per minimum.
Then again If you are just getting what’s off the shelf due to cost issue you may not have that choice.
A few Polyesters are now being backed with something called EPO, not really sure what it is EXACTLY but I do know it has a more to do with rubbery feel than PU. It is more expensive and heavier.
Also look into foaming PU’s. Instead of laminating with a spray or dip the laminate has hot air blown into it creating a thicker yet lighter matrix that has the performance of 2 or 3x PU but at half the weight without killing the normal stretch of Poly. Really lays nice even on the crappiest 190D’s. be careful tho, PVC comes this way as well.
One of my clients just dropped all PVC backings in favor of PU and EPO and saw their material costs jump almost 10-15%.