If the request is coming from your supervisor and it is something work related, such as a project status check up or a customer expectation etc, it is best that you choose the best time depending on the project's timeline. Your supervisor might not be aware of your position on the subject matter project and deferring the timing to you, so that you can be more prepared.
If it is a personal matter, like your yearly or quarterly review, it is best if you choose a time which you know will be better for your boss, indicating that you are available for all the time slots offered but you thought it might be at your boss' best interest if you go with this or that time. This will make you sound decisive, at the same time considerate of your boss. And letting your boss know that you are open to all suggestions, gives them the chance to offer a different time, should he/she feels another time slot serves better for his/her purpose.
On the other hand, if the meeting request is coming from a coworker or a project team member, it has almost always been my experience that, more flexible you sound, more irrelevant work you end up getting during the course of the project. Choose one time slot, even if it is at random, and stick to it, and if necessary, resist the time change proposals, within reason of course. If someone, who is not your boss, thinks that he/she can walk over you, this is not a good move for the rest of your time in that position.