I've joined a startup an year ago as #1 full-time employee (the team is small, we're 5 employees and the 3 founders), and at the beginning we've stated a pretty small percentage of equity (less than 2%) after a two years vesting and some other conditions.

The team is great, the environment is cool but the future is uncertain. In this year I've added a huge value to the company and now I don't think that the equity we agreed on are fair.

At the moment the company is going through an hard period (the marketing seems to be not so skilled) and I don't think we will meet the goals. Not sure if we're going to make it through another couple of years (and I'm probably not going to take any equity at all).

Last week another company called me for an interview and I accepted.

In case of an offer the only thing that will probably make me stay is a bigger and immediate share (4-5%), because if I have to sink with the ship I don't want to sink as a sailor.

Is that a fair reasoning or it sounds like a threat?