I don't see why it would matter one way or the other really. But what you can do is answer it both ways (one way at a time of course) and see what, if anything, changes. As for an "annual increase", that would not be a bonus. If it had to be labeled anything, that would be a raise.
In general, an "annual increase" increases the income of all employees. Whereas a bonus is only paid to certain employees.
Generally, raises are included in box 1 of the W-2. For a bonus, it may or may not be included in box 1. When it's not, I've at times seen a bonus reported separately on a 1099-MISC. In some situations (which I'm not that privy on) a bonus may be taxed differently than "regular" pay.
