I use a set of Ultra Jazz in my four-string fretted bass, and a set of Model Js in my four-string fretless - and I would say that each model is well-suited to the application I've chosen for it.
IME, the Ultra Jazz is mildly mid-scooped, but not nearly to the point that is commonly stated. It's brighter, more modern & more refined than the Model J, with a really lovely tone that works well in a variety of genres - modern rock (not so much classic rock), funk, pop, jazz, etc. It offers a great slap tone, in case you're into that sort of thing.
The Model J is definitely more aggressive, with a somewhat rolled-off top end, and thicker mids, relative to the Ultra Jazz. Both pickups have good, strong low end, but the Model Js is especially good for cranked-up, high-gain, fingerstyle
rawk. Because it's rather hot, with such strong mids, it also works really well for fretless bass - especially if you favor a big, powerful tone that can compensate somewhat for the naturally more subdued tone of the fretless.
MM