There's huge variability among startups.

There are small startups; no one knows whether these will succeed, even if they're YC startups.

There are big(ger) startups that are clearly on the way up. Pinterest. Dropbox. Airbnb. Uber. Snapchat.

Then there are medium sized but fast growing startups. Quora. Stripe. etc.

The latter two categories are obvious choices.