I’ve never heard a diamond cantilever, or know anyone who has one.
but all the signal generating works are at the other end, so info must be transmitted, lightest/stiffest best by theory, and by maker’s literature and ’top of the line’ models.
The jump up in price from boron or sapphire or ruby colored sapphire is huge, I certainly would not spend for a new one
but, you have an opportunity to try the stiffest material at a rebuild price, so I would ask their advice/price.
I experienced the best/tightest bass in my life with Shure’s V15VxMR original stylus with beryllium vapor deposited microwall tube. It was the cantilever that made all the difference. When I broke it, it turned to dust before my eyes, sad day for sure.
file:///C:/Users/elliott/Downloads/V15VxMR_guide_en-US.pdf
On SME 3009 II arm, on Thorens TD124, incredible. And, it tracked at 1.0g! I’ve got my eye on an OEM Stylus currently, I might get lucky.
Today, materials are rods, not tubes, so we need to risk used to get these rare tube cantilevers.
btw, AT33PTG, orig and II, and new AT33x are TAPERED Boron rod, I would choose tapered over rod in any design, just by instinct.
look at the comparison of rod/tube/microwall in that Shure document above.

