But by withholding you also increase the risk that your first block will never end up in the main chain (if the remaining 90% find a block while you're withholding).

And you would sill have 10% chance of mining another block if you don't withhold.

What advantage does withholding give you?

> What advantage does withholding give you?

One last time. By withholding, you have a headstart on the next block. If you can mine for longer, you increase your chances.