These programs are very different from each other. Y Combinator is obviously the more successful one with multiple companies of over one billion dollar values, whereas I don’t believe TechStars has had one company over a $500 million dollar valuation (not even sure if any are over $100M, maybe Sendgrid). That being said, I think the organizations aren’t directly competing for the same type of companies to be in their respective accelerator programs. I think the makeup of the companies that should be applying to each is at quite different stages of maturation.
My experience has been with TechStars NYC, so I’m not sure this also holds true for Boulder, Seattle, and Boston, but the most successful companies that enter TechStars are product ready and looking for biz dev/partnerships to grow the business. They have their product, probably have found product/market fit, and would like to use the TS network to take it to the next level- to accelerate their business.
In my experience, YC is the right accelerator if you are still in the product development stage. They make bets on high potential teams. Teams come in with one idea and those ideas evolve. Some companies are not even ready by demo day- but the lifetime success rate for those individuals is very high. You are typically not focused on partnerships or distribution deals- you and your team are heads down focusing on building a killer product.
While I’ve never been in either program, I do have many friends that have and this is the sense I get.
I think that both accelerators are great and amazing for the startup world. One thing I’m still waiting to see is the first company that starts off in YC for product acceleration to then go to TS for business acceleration :) :) :)