Two things compared to Liberapay:

1. It allows one time donations and recurring instead of just recurring
2. It allows for transparency in how the money is spent and where it goes.

Compared to Patreon you can also add in that it is FOSS like Liberapay.

These are more positives for the end user or donater rather than the project so i can see how they wouldn't sway everyone. I wouldn't say you have to use Open Collective instead of the others, you can use it alongisde if you wanted. Just food for thought.