The 9000 points upgrade is great value at many hotels. Asking with points or voucher (f.e. Harper) stays is also a good and often the only option to "save" such stays. Option (even without negotiation) is also the paid option in advance with Hilton (if you stay in one of the very few interesting Hiltons)
With a regular stay itīs different, many hotels will tell you in advance that you should book the suite if you like it, In most cases it may be more promising to ask a check-in or (what I sometimes did in my student times) to say when you are shown the room you think itīs too small or whatever. Often you will get a free upgrade or some discounted. Of course itīs a little bit laughable to be shown a 100 sm suite and to tell them it feels tiny when aiming on the Presidential Suite