Kid,
First, OAL length will vary some because the seating stem in your dies are not pushing directly on the end of the bullet. They stem is pressing on some point on the ogive(curve, for lack of an easier explanation) of the bullet, unless its a semi or full wadcutter. The bullets will vary slightly.
Second, the OAL of a semi auto cartridge should not be determined by a manual. It will be determined by what feeds in the gun. I can't think of the last time I measured the OAL length of my 45 Auto ammo but I will bet it would vary as well. However, I do know that it feeds in my guns all the time.
My advice is to get a loaded cartridge gauge and make sure everything gauges. Some will tell you to use your barrel but i don't recommend it for two reasons. One, it doesn't gauge the complete cartridge. Secondly, and more importantly, at some point, the possibility of you getting distracted and accidentally having a live round in your gun when you don't want it to be there. Phone rings, wife hollars from the house, neighbor pulls up.
However, back to your question. If you use the OAL length from the manual, slightly shorter would be better. That way, when you do have that long bullet, and you will, it will still be short enough to feed.