I like the JDI for the way it connects to a speaker signal in parallel, and for the way it has no active circuitry to worry about.
With the Countryman I have to keep a 9V handy in case phantom power is not available. (And while on 9V be careful plugging & unplugging from the "input" jack - it will send a loud "pop" through the XLR. Most PA owners really hate that.)
I did a bunch of testing and found my JDI sounds noticeably worse with my passive basses going straight in. (Less treble, not as even, just kind of "stale" overall.) It would of course be better than nothing in a pinch, but I would definitely prefer to insert a good active buffer circuit before it (onboard pre, outboard pre, rack pre, amp, etc) or use the Countryman.
IME passive basses respond more naturally and musically with the Countryman and for what I could get for my beat up unit, it's probably worth hanging on to for those times where I might want a clean, unaltered capture.
What I really want to do is add high quality tube character to the DI signal and maybe some tone adjustment, but still have a separate control for stage volume. There are of course multiple ways to achieve this, with varying degrees of convenience and expense. (Hopefully the 1/4" line out from my 50W tube amp to the JDI will do the trick. May have to patch together something different for louder applications.)
I could always give up on the separate volume concept and that would open up a few more possibilities. (Like the post-power send, the speaker signal, or not least of all a mic.)