Booking ahead or not is always a personal decision. Pros and cons of both have been pointed out. My husband and I have had the experience of booking ahead and then not being able to get there for one reason or another. Most of the time, a call direct to the lodging place will be a little easier and more personable when explaining your sudden change of plans.
BTW, the above experience is because we ONLY book through either the website of the hotel/hotel chain, or by phone. We do not use third-party bookings (Expedia, Hotels.com, booking.com, etc) if we can help it. It is WAY too difficult to change your plans mid-stream through a third-party, who typical sell hotel rooms that they may not have filled otherwise.
Another reason not to use a third party: upgrades. On our recent trip, my husband and I were engaged in a conversation with a BW manager. He gave us priority in rooms on request, because we had been members of the BW Rewards Program for a few years. (We like first floor rooms in properties with no elevators mentioned on their website, though the photo shows two stories.) He stated, "I'll go out of my way to upgrade a Rewards member and honor their simple requests, because they're obviously a long-term customer of the company. Those who use third parties are out for the cheap rooms, and we've had issues not being respectful of our property."
Donna