performance curve distributor

Is it worth the extra money for a aftermarket distributor with a "built in performance curve"? I understand that the distributor is just a trigger for the spark but, I can't help wondering if my autozone vacuum advance distributor is not up to par for my msd box and high energy coil.
Also, what are the issues going from vacuum to mechanical advance? I want to get the best performance with good street manners. I've been looking at the mechanical msd billet for around 200$. Would this be a worthwhile upgrade or am I just throwing away money?