OK, reporting back...The TIs are on a custom ACG with fancy EQ but I've been running it in passive as the La Bella's are on a passive ACG. Both basses are fretless, both have two humbuckers and both have ebony boards. Somewhat different body woods though.
The feel of both sets under the digits is pretty similar as they have pretty much similar gauges, maybe the E string feels ever so slightly different. Tonally I'd say the La Bella's, to my ears, are slightly warmer sounding, and maybe do the treble slightly better. The TIs though do seem to have stronger mids. We are not talking about chalk and cheese here, I think the differences are noticable but don't slap you in the face so to speak.
On balance my preference is for the TIs, even though they are a chunk more costly. It's hard to rationlise in any objective way, I just prefer the sound of them I guess.
As an aside, I'm going to take the La Bella's off to keep them in good nick as they may well be of interest to others...PM me if you're interested otherwise I'll stick them on the marketplace.