I own the ti version and have handled the aluminum version at a dealer. Personally, I like the ti (original) version alot more than the aluminum version. The difference? Smooth opening/closing (ti) vs. okay (aluminum). The blade grind on the ti seem to also have smoother edges (e.g., the transition from the hollow grind to the spine). And if my memory is correct, I think the ti has no (or fewer) visible screws holding the handle together vs. visible screws on the aluminum Herbst. Caution: It has been reported that some (or most) ti Herbsts were defective coming out of the factory and consequently were not readily available in larger numbers in the market--which speaks volumes for Spyderco quality control which ensures that the ELU will rarely purchase a lemon. Mine had some minor cosmetic flaws and who knows what else that did not meet Spyderco standards but I love it just the way it is anyway. (Others might feel otherwise).
I suggest that you try and handle both (if possible) before buying the aluminum handled Herbst. However, you will probably have to scour the secondary market--eBay, forum knife exchanges, etc.--should you decide to opt for the ti Herbst.
Is this a biased review? Uh, yeah.