Its a proven fact that the X 4.6 series plastics are more brittle than the older 25 series plastics. HPI even says the forumla is lighter. If you wanted to upgrade the a arms to stronger ones the older a arms do not break near as easy.
If it's a proven fact, show me a citation. I have not seen any documented tests on this forum or any other. Also, show me where HPI claims that the new plastics are less durable. I'm not discrediting your statement, just asking you to back up your claims.
I do agree that the new X arms are much less durable, but I feel this is related to the removal of material around the hinge pin area, and not the plastics used. I run original arms.