I always shoot for a consistent AFR across all RPM and load points. Theoretically it should be a flat line at the AFR that your engine makes the most power at. But there are so many variables (advance, VE, RPM, load, etc.).
Yes, I have Access to (wish I owned) a DynaPack. this allows you to set a fixed RPM or load band and the dyno will hold the engine at that point. We start with a generic timing table with a conservative max advance at WOT. We typically work on one RPM band at a time, and then tune each load bin. So when you are done with one load bin at a given RPM, you press the throttle a little more until you get to the next load bin. You keep repeating this until you reach your max RPM or it starts getting too hot (let it cool down and continue). Once all the load bands are tuned then we will do some max power pulls and fine tune max power by adding advance (gradually) and monitoring AFR. So add a little advance and a little fuel at the same time. You will eventually reach a point where it is either detonating, or it isn't making any more power and the AFR is getting rich.
My rule of thumb is 14:1 for NA and 12.5:1 for boosted.
So to answer your question, once you find that "sweetspot" AFR for your engine, I would shoot for a flat AFR curve in that region. Just add a little safety margin in your spark advance and AFR so you are not blowing head gaskets.
Pete