Actually, titanium is 40% lighter than steel. I handled a Caspian gun built on a titanium frame at Shot Show, and it felt pretty good. It was noticeably lighter than the all steel version, and the guys at Caspian said it would hold up just as well. Also, titanium isn't as susceptable to temparature changes as steel. So, in cold weather, the titanium doesn't feel as cold, and in hot weather, it doesn't feel as hot. Down here in Miami, that's a consideration. I would recommend having a gun built on Caspian's titanium frame with built-in light rail.
Hope this helps.