I have 2 sbc....a 406 which sees 7200.....and a 342 which sees 8500.....we went with a stealth titanium valve[only in the 342] on the intake +100 in lenth because it is lighter,which enables the motor to rev quicker and it is stronger,which is necessary when you are going to see 8500 rpm plus......alot of the import guys put the titanium valves in because those lil v-tech motors spin as high as 12,000 rpms....
titanium is stronger and lighter than steel,but in my personal opinion,unless you have a race car or in a situation you are running very high rpm,its a waste of money at as much as 1800-2000.00 for a set of titanium intake and exhaust valves.
the comp eliminator racers we worked with on the 342 also discouraged us from using the titanium valves on the exhaust side.they said because of the excessive heat the titanium exhaust valves tend to stick.....so we only used titanium on the intake side and steel manley valves on the exhaust side and went to +100 on the lenths of both.