which would be a better investment for a bike frame?

Neither. Steel is REAL! http://gunnarbikes.com/site/

Are you going to put the frame away and then resell it in a decade. That is an investment. If that is the case, then titanium because you can at least melt it down and still have the metal.

If oyu are talking about which is a better buy for a bike you want to build up, then the answer is whichever frame is better for you. Some people swear by titanium, some really dig the stiffness of a carbon frame. Of course, there are lots of variations in carbon frames.

It's not that simple...

Lets first define a "known manufacturer". Most brands don't make their own carbon fiber OR titanium frames (or anything of their own) so if you are relating "known manufacturer" to "brand" then you may be placing your trust a bit loosely.

Both carbon fiber and titanium have specific manufacturing procedures that must be used to make a good frame.

For example, if titanium is contaminated while machining or welding it, or if the "prepreg" carbon fiber cloth is out of date either material can fail in a hurry. BOTH of these scenarios, although not common, are possible and a specific brand name is not assurance that they don't occur.

As far as longevity, a Ti frame will far outlive a carbon fiber model regardless what anyone says about racing cars and airplanes, and will handle bumps and bruises with much better result. Carbon fiber as a material may last forever but when combined with epoxies and stuck together, well, the structure will not.

The best way to make your choice is to look at each frame EVEN IF you know nothing about each material. If you see wiggly lines in carbon fiber seams (usually located on the BOTTOM of each tube) or if there is unevenness in the welds of a Ti frame then you should continue to look.

The people that make these things take great pride in their work and would never allow such sloppiness to leave their shops.

this will be so expensive, you should already know what you want the frame to do

if you did, that would answer your question

also

i would not trust carbon for anything

ever

i know it can last a few years

i don;t want to be worried about how many

and scratches

bumps

sun

age

wle

Investment? I would suggest that you talk with custom builders.