I've had the lot, Mick, from high-end custom-built jobbies (built for someone else, mind) down to B-stock Thomann cheapies.
In truth I love 'em, but only for the right project. I've used them for steampunk folk bands and for amateur-night Americana bands, and of course for jam sessions and frontroom parties, and they're absolutely right for all those jobs.
IME by far the biggest difference is to do with string choice. The cheap nylon/rubber strings (like the ones on your old Ashbory) are a PITA to use, more so to tune, and above all to change; plus they give you such a flobbadob sound that they reduce all bass players to the same level.
Unlike Jean-Luc, I actually prefer the Thunderguts to the Pahoehoes, but they're still nylon/rubber. Top tip, take a small can of talcum powder in your gig bag, use liberally before playing.
The new Kala roundwounds (well, new two years ago) are a complete game-changer. They make a U-bass sound and (to some extent) play like a 'real' bass, if that's what you're after.