One can never have too many tools. Well, at least I don't think so. I haven't used a swept back grind in many years. To me, and part of this is because I did production work, the swept back grind is a 'does every thing' type of tool, so one gouge can do pretty much every thing required to turn a good bowl. After learning the 40/40 grind, I no longer use the swept back grind at all. Main reason is that the specialized tools do the better jobs. The 40/40 for the outside of the bowl. The 40/40 for the walls on the inside down to the transition, and then a BOB (bottom of bowl) tool for the transition and going across the bottom. I use scrapers for all of my heavy roughing.
I have tried smaller gouges for finish cuts, and maybe it is just me, but I don't get better cuts with them than I do with the 5/8 gouges which are my work horses.
robo hippy