Wow, quite a discussion here! I’ll address questions as best I can from a sound engineer’s perspective.
When I put a DI on stage, it needs to be dead simple, rugged, and clean. The stage DI is simply a way for a musician to plug their instrument into the PA, and thus should not affect the tone in any way. I also don’t want a DI that requires a power supply transformer eating up sockets on my stage power strips; it must be passive (like the Radial JDI) or powered by phantom power (like the J48 or Countryman 85). The REDDI is big, heavy, expensive, and requires AC power… So unless I need it as a specialty item in a show, it’s not going on stage to get stepped on and tossed around.
In the studio, we have more options. The REDDI produces a big, clean, clear tone that, to my ears, sounds magnificent. It imparts some subtle harmonics (the “big”-ness) that are pleasing, but mostly just sounds like an immense but clean tone.
I had a Mesa Subway DI+ briefly, but returned it. It was noisy, muddy, and seemed to have a permanent high pass filter around 50 Hz. I can’t speak to other preamps, as I haven’t used them. As a studio engineer, I’m not going to provide a LeBass or Tone Hammer, etc, as those are more personal options, and I don’t want to buy one of everything to suit an individual musician’s needs; if that’s part of their sound, they should bring one. However, I also want as clean a tone as possible, so I can adjust as needed to get it to fit in the mix.
Anyway, whether the REDDI is worth the money to you is a question only you can answer; I’ll provide the sound samples, though, to help facilitate that. 