I find it much more fun to meet friends at a restaurant without a reservation. Less obligation to follow through. If one of us has a last minute idea to do something else, we go with the flow. If none of the available tables are to our liking, we go with the flow and go elsewhere. If there is no available table, we go with the flow and go elsewhere. So much more serendipity and freedom.
One time, we arrived at a restaurant and were told that there is no available table. Since I just read in a book that you usually can bribe the waiter, I jumped over my shadow, said "Maybe we can wait a few minutes and see if something becomes available?" and put a €20 note into the hand of the waiter. Pointed at the best table at the window and said "That one would be perfect of course". 5 minutes later, we were sitting at the table at the window. I was a nerve wreck and felt like a king :)