You'll probably find strong feelings on both sides of the fence on this one. I own both 2 band and 3 band Stingrays and 4 string and 5 string versions and have played a number of H, HH and HS Stingrays. Here's my opinions FWIW:
If you want the old school preEB sound there's only one way to go - single H with 2 band preamp. You can get that in a used SUB bass with 4 or 5 srings for less money than a new or used Stingray will put you out.
If you want a more modern sound that is in the Stingray ballpark but has more flexibility and tone options - go with the HS 3 band.
If you want a Swiss Army knife of basses - go with a Big Al 5 sring or for less money pick up a used Bongo HH 5 string.
There is a huge difference between the MM 2 band and 3 band preamps in my opinion. My personal preference is the single H 2 band 5 string configuration (I just like 5's from a comfort standpoint, the 4 string sounds just as good). I find I can VERY quickly zero in on a specific tone with the 2 band preamp - usually I keep the bass knob on about 75% and the treb on about 25% and then bump the treb up or down as needed for room acoustics or song changes. With the 3 band preamps I find myself constantly hunting for the right tone and rarely finding it quickly. With the 2 band it's literally a 1 or 2 second fiddle with the tone knob, no problem with mid song or solo adjustments. With the 3 band, I wont touch the knobs unless I'm between sets and then it can take a minute or two to really zero in on a setting that will be perfect for the mix.
Oddly I do find the 3 band to be more mid focused than the 2 band. My 2 band Stingray preamps can go both lower and higher than my Stingray 3 band preamps. That's not the norm for my other basses (i.e. Fender, Warwick, Pedulla, etc.) on those basses 3 bands means broader spectrum, I just don't get that with my 3 band Stingrays.