No you can't, yet. The statistical sample is much too small to determine whether Techstars is on par, higher or lower with Harvard comparatively to make this statement.
Sure Techstars might be amazing in a hundred years time, but it's not exactly relavent for someone deciding what to do now.
Is HBS designed to produce tech startups though? HBS is probably closer to their desired results by virtue of "refinement" of it's aims and processes, yes. However unless those aims include "creating more tech startups" I don't see how their longevity is especially relevant.
If Harvard is better at producing startups than TS, regardless of the reason (alumni, experience), then Harvard would actually be a better choice than TS for someone looking to found a startup.