> I've never seen #s on Techstars as a whole
Here are Techstars Stats:
There is no way to quantify which one is better. YC has some companies that happened to hit it big. Techstars has some that are doing very well, too.
Both get great companies applying, so while the accelerators help and are valuable, it's the founders that are still doing the hard work of building the company.
Is Harvard truly better, than, say, Cornell, even if it's ranked higher. Let's say that Harvard has the benefit of getting better people overall, since it has better brand name. So an average Harvard student is marginally "better" than an average Cornell Student. Let's say that after you do a study of outcomes, you see that Harvard graduates do better than Cornell graduates. Is it truly due to the school's effect, or due to one school getting better students as inputs.
Both accelerators are very selective. If you can get into either, that's a pretty big endorsement and you should think seriously of doing the program.
One thing I will say, to continue with my analogy, is that one school may be better than the other in a specific area of study.
I am more familiar with Techstars, having gone through the Kaplan EdTech Accelerator powered by Techstars, and want to draw attention that if you are in one of the verticals that Techstars has a program in, it may be better than YC. You'll be surrounded by other companies in similar industry, mentors with experience in this area, and hear from founders that found success in your area. You will also get access to the sponsoring company, which can give a huge leg up.