I switched to 5ers back in 1990, and haven't owned a 4 since.
I think for most, the "camp" you find yourself in has to do with what music you set yourself up for, and what you consider convenient. I mostly play a wide variety of covers, so I never spent time focussing just on what tunes or types of music my "heroes" play, and modelling how I equip myself after them. When I saw that some tunes needed notes lower than E, I considered what my options were. For me, it was illogical to have a device on a four-string that flatted the E string so I could have a whole step or whatever just for one song (or however many), and while I was doing that have to get used to the different interval between the E and A strings. Nor was I ever interested in or required to play tunes that were all in flatted tunings (heavier guitar stuff -- metal and all its variants, if you will) -- not my cup o' tea.
So simply having an extra string with the same intervallic relationship as the others seemed the best way to go, and in the widest examination (IMO) of the current state of popular (non-classical) music, it seems like it was a good choice. I've never like the idea of switching back and forth between instruments during a gig (no time), and I'm not in so many bands that I feel like I've got to assume a different "bass identity" in each one. So, different strokes, I guess.