For those saying, "absolutely no reason not to," go read up some on Browning HiPowers and loading 13+1 with original mags. This can (and often did) result in function problems.
So, whether to load +1 or not, IMO, depends on a few factors.
For instance, does the manufacturer recommend loading to capacity +1? (Some owner's manuals advise against doing this.)
Does the weapon have a reputation for proper reliability when loaded to +1?
Assuming the answers to the first two questions are "yes" and "yes", then -
How has your weapon functioned during extended range sessions when consistently loaded to capacity +1?
Oh, and for those yelling at the OP about "an empty chamber is an unloaded gun!" next time try reading more carefully. He never mentioned an empty chamber.
(Edit: He did mention another factor that I do sometimes take into account - if I know I am going to have to unload the gun, I don't like having a loose round. For example, I normally shoot my carry gun at IDPA matches. I know, going in, that I will unload the gun prior to entering the classroom before the match begins, so I don't load +1 if going to IDPA. I do chamber a round, but when I unload, the chambered round has its place in the magazine.)
(Second edit: When this occurs, I unload the mag, and put the previously chambered round in first, so it becomes the last round. This fends off bullet setback for quite a bit longer.)