How much of a barrier does a login screen pose for a SaaS?

I've encountered 3 types of flows for a SaaS:

1. Everything behind a login including free tools
2. No login is required for a free solution
3. Hybrid where you have free teasers but the general product is behind a login or you fill out a bunch of prompts but the end result is blocked behind a login

What are your thoughts on these flows?