Which cantilever to choose for re-tip

I have two cartridges I plan on having re tipped by Soundsmith. One is a Shelter 501 II, and the other is a Lyra Lydian B.
Both of these came originally with boron cantilevers. 
Is it worth the $450 each for the boron or should I go for the $350 ruby? 
Why not call Ledermann and ask him about it? The carts are different enough could be one is more suited to one than the other. If anyone would know it would be him.
Just remember, it’s NOT going to be the same cartridge afterwards.

To your ears, it could be better, different,same or anything in between. It will be a glued on to the stub of whats remaining from the original.

I had a Sumiko Blackbird done with the ruby. I actually liked the presentation more than the original. I eventually crashed that one too. Moved on. My awareness to be cautious anytime I’m around the table, has grown since then.

Personally, I would save the $200, and get the ruby.
Dear @jsbail : With out doubt you must go for the boron cantilever. At the ened the manufacturer designer decided that those cartridge models gone with boron cantilever.

Regards and enjoy the MUSIC NOT DISTORTIONS,
If you are a klutz most definitely Boron. Harder to break. Millercarbon, stick with your Koetsu and get off that "jitter" merry-go-round. Ledermann could never tell what these cartridges really sound like because they "jitter" too much. Imagine that, fixing all these jittery cartridges so they can "jitter" some more. Lets call up Lewis Carroll and have a tea party. 
I would leave it up to Peter.  Both times I sent him carts he felt the best way to go was to just replace the stylus on the original cantilever.  And yes, he used what appears to be a blob of glue to attach it, but the carts sounded absolutely great when I got them back.  I can't tell you whether they sounded identical to the original, but I was very happy with the sound.  
The best philosophy is to stay with the original cantilever material because the cartridge was designed and built with that choice in mind. So your answer is “boron”. This has nothing to do with one being “better” than the other. 
By the way, I am only quoting the advice of Jonathan Carr, who designs Lyra cartridges for a living.  He also pointed out that there is a significant difference in mass between boron and sapphire, which would have led the original designer to choose different materials for suspension and damping of boron vs sapphire, etc.
Shelter makes great sounding cartridges; I just wish they had a rebuild, retip, or at least an exchange service - but I've never heard any examples of such a thing? 

What's a shame is that a brand new 501 Mk III costs only like $1000 or so from Japan, right? The $450 boron retip would get you back a Mk II at best, and that's close to the 50% cost of a newer Mk III that you'd expect to get back from a rebuild service (if Shelter had one price-structured like Ortofon and Koetsu). And of course the ruby cantilever will definitely change the sound, maybe not for the better. I don't like either of those options. I'd probably try to see if another retipper can keep boron for less money, or I'd get what I can for the 501 as-is by hocking it, and then buy a brand new Mk III from Japan.
Ok. Seems boron is the way to go on the Shelter. More than half what I paid for the cartridge but still seems worth it if it sounds great when repaired.
I decided to have them evaluate the Lyra. The stylus looks fine but has turned sideways. The cantilever is loose. I hope they can glue it.

FWIW, I chose boron for my Benz Ebony LO, which is what it came with, and I'm very pleased. Sounds like stock, which is what I wanted.
I can't swear to this, but I do believe the Mk3 was at most only a few hundred bucks more than the Mk2 (not double the price of a Mk2), last spring when I was in Tokyo.  It may even have been the same price.  I eventually bought a Mk2 Mono.
 It turns out the Shelter could not be repaired do to suspension damage. My fiancé was trying to do me a favor by dusting. Married her anyway.

Going with a boron cantilever on the Lyra.