I have thought about this a lot and done some research on it. Bear in mind, I'm far from an expert, just a curious dev, but I've found no reasons to favor GPL over AGPL when AGPL exists. I personally see AGPL as closing a loophole GPL didn't think of.

One thing I'd wondered if if maybe AGPL hasn't been tested in court. It has. Not as much as GPL, and I don't remember if it specifically was the online part, but I definitely found at least one court case involving AGPL code.