To me, metal ones sound buzzy and a bit dull, and ebonite ones sound like you're blowing through a sock.
Having said that, my favourite mouthpiece is a metal link. It's been modified to the extent that even Nick might approve flattened table, evened out rails, size 10 tip opening and a massive step baffle. It's the mutts nuts, and about as far as it's possible to get from a standard Link as is imaginable.
That's right Nick. I gave my metal one away 'cos on recordings it just didn't cut the mustard for me. It sounded great in the shop, but the way we think we sound and the actual sound, can be way off!!!!!!!!!!!!!!!!!!!!
Well, no. But, like everything else in music, it's all about what appeals to your own ears. To my ears, warm = dull, but I'm assured that this is not the case for everybody. And I'd be the first to admit that if every tenor player sounded like me the world would not be a better place. So, whilst I would not wish to sound like Stan Getz (for instance), I quite like to listen to him and I don't begrudge anyone else wishing to sound like him.
There are just so many mouthpiece experts that produce improved versions 0f metal and rubber links, or produce accurate replicas of original links that it is worth concluding that modern versons leave a lot to be desired and are not of a very consistent quality.
There are also alarge number of high quality mouthpieces out there, which were not available in times of yore, which are probably of far better quality overall. Some older saxes are thought to have a special sound, but I think that we have to be careful not to glorify such vintage items. I've never particularly wanted a Link, but have tried an STM on both Tenor and Alto. and thought that they were passable, not awesome. My teacher used to play a Link Tone Edge rubber, but was happier with his new Jody Jazz HR mouthpiece.
Of interest might be a 9 Tenor Sax Mouthpiece Poll on Steve Neff's wesite, which had a modern Link votes last. If you Google "Steve Neff Poll of 9 Tenor Mouthpieces" you will be able to access sound clips etc. The modified Link mpcs do better than the Modern one - so it may be worth looking up some of the replica or reworked Links if you have to have one.