jubuttib said:
All things (shape, size, weight) being equal there's no difference in the flight between Z and Ti. After those things the only thing that really could affect flight would be weight distribution (I'm assuming Discraft's blends are at least somewhat homogeneous and the density of the plastic doesn't vary across the disc significantly, so that's out) and to an extent surface texture. There might be some microscopic difference between Ti and Z surface textures, but they're so small I really doubt it'd affect the flight in any way.
To nitpick with your point slightly, you seem to be suggesting that any material with the same given density should make a disc with the same shape, size and weight fly identically. My experiences obviously differ from yours with regards to at a minimum the Ti Buzzz. I intentionally got flat and heavy Ti Buzzzes, as those are qualities that have led me to select Buzzzes in other plastics, with some regularity as to my expectations. Mine, along with those of others I have talked to (not a mammoth sample, but let's say 15 other golfers, ranging in skill from Rec to 1000 rated Open players), are less stable. There are certainly a number of factors that may account for this, but I am not just making this up. In general, most of the Ti plastic discs seem to be more overstable than the other plastics. The Ti Forces are the only mold that seems to be shaped differently, from what I have seen.