Finally managed to have a fiddle. Full disclosure, my basses are all set up with a very low action and have ramps, so my playing style involves a light touch. Brief verdict (IMHO YMMV etc):
Boss SYB-5: Great sounds, mightily close to what I want, but far too glitchy.
Future Impact: Amazing pedal, but to get the best out of it you have to buy more gear. Again glitchy.
Digitech Bass Synth Wah: I don't want to say how great this pedal is, in case you all go out and buy one, 'coz I'm certainly going to buy another 😆! Flawless tracking, useful sounds, not glitchy at all.