In a very cursory search on the net, I confirmed my assumption that titanium is weaker than hi-strength alloy steel in terms of yield strength based on cross-sectional area. AFAIK there is no reason a titanium spoke of larger diameter couldn't equal or out-perform a steel spoke, but if is constrained to the same diameter it will probably be at a disadvantage in terms of fatigue life. For better or worse, it will also be more compliant, by approximately a factor of 2 for the same diameter, as steel, according to data I just googled.