Safari sling is the most comfortable and I get why people like it. I am not a fan of the safari sling for several reasons though. 1, its very bulky 2, the “loop” over the butt slips off if you ever hold the barrel down, so its much less versatile, 3 the loop over the barrel tends to get hung up more, 4 “horizontal” is the default and almost only position it works, which I dont like if around other people at all. In hunting for the past couple decades I think Ive had guns pointed at me more from random dudes in the woods with safari slings than I have all other instances combined. Perhaps not a “requirement” of the sling, but its definitely not designed with barrel up or down in mind.
For my use I prefer no sling much of the time, but I also want a sling at times for glassing while still-hunting, tree-to-tree up a steep hillside while on a track, etc, as well as for a long dark walk home. For me the flush cups provide by far the best versatility (traditional vertical carry, chest vertical or horizontal, tight or loose, shooting support, etc) while maintaining best size to keep in a pocket or pack lid, and easiest on/off in the field.