For cosmetic longevity it has to be Ti surely? Can only imagine what a carbon MTB frame would look like after 5 or more years use.
To be honest if I was buying again now, I'd more than likely go for decent steel instead of Ti or Carbon.
I think a high end steel frame has got to be better than a low rent carbon frame.
Ti is amazing stuff, keeps it's looks over the years no matter how much abuse. My 93 Hei Hei proved that, still looks new even after all this time!
1993 Kona Hei Hei, 2013 Mutiny Robbo X-Sekt, 2006 Rocky Mountain Blizzard, 2007 Mongoose Sabrosa 29er, 2016 Transition Scout, 1998 Mk 1 Standard Trailboss , 2013 Salsa Vaya, Player Special - 2015 Ted James custom roadie