I already have 3 Stingrays, the thing that attracted me to the Z7 was precisely the Jazz pickup together with the passive tone always in the circuit.
Is it worth it? I've played single pickup Stingrays for years, and managed quite well, so it's not like the bass is lacking anything. But I like what the Jazz pickup brings. One of my favourite tones on the Z7 is based on adding a bit of the Jazz pickup, just when it starts to become noticeable plus a gnat's baw hair, cut all treble on the active EQ, and bring the passive tone down to taste. Fat but very articulate sound. That means... I'm a fan
In addition, the necks on these basses are soooo nice. I've played instruments with rolled fingerboard edges, but this is top level. It's making it very difficult for me to want to play anything else
So, I'd say Z7... but the heart wants what the heart wants, and I bought my purple sparke SBMM Ray35 despite being able at the time to buy a used 90s Stingray5 for a couple of hundred quid more... because purple! sparkle! It's a heavy beast. The Sire Z7-5 that I've got is 9.0 lbs, another factor that is making me like it more and more.
Another thing, if you're talking about the 4-string... I have nothing to add. But the 5-string versions look like they have different string spacing, with the Z3 being the one with the shorter spacing. The Z7-5 is 17.5mm at the bridge.