I'm in agreement with VTHillman's above comment.

It really depends on whether the magazine and pistol combination are designed for a +1 load out.

Some designs don't have enough room to allow the top round in a full magazine to be compressed further, as is required when the slide is in battery.

That said, I carry +1 all the time, as I won't carry a pistol that can't be loaded to +1 capacity.

It's more than just a capacity issue. If it won't accommodate a +1 load in an administrative reload, it won't tolerate one in a tactical reload either where you may be dropping an empty or nearly empty magazine and reloading with a round constantly in the chamber. An inability to easily insert and positively seat a full magazine into the pistol with the slide already in battery is a serious tactical disadvantage.