To reply to myself, I took a look using Tes4Edit to see what Slof's BB and Roberts Male we're both doing. Roberts points to the "non-standard" location for the Argonian tail mesh (/meshes/characters/argonian/male/tail.nif), while Slof's BB "corrects" that and points to where it installs the spiked tail mesh (/meshes/characters/argonian/tail.nif).
All should be fine with Slof's loading after Robert's; however, my BASH patch was overriding the changes done by Slof's. This is using the default suggestions of BOSS (Graphics, NpcFaces, R.Teeth). It seems logical that Body-F and Body-M should be added to that list as Slof's does, in fact, make those changes. Sure enough, with those two tags added, Argonian males are beautified.
Would adding these tags to Slof's BB introduce any problems? It seems that those tags should have been recommended by BOSS given what Slof's changes, but I'm still very much in the learning phases so I can't be sure what seems logical to me might not cause massive problems elsewhere.