I've had my BB424 a couple of weeks now and I'm still extremely pleased with it. I've carried on listening to as many youtube demos of the various models as I can bear, and feel that, for the sound I was wanting this was exactly the right model for me, not just against the 414 and 434, but even against the more expensive Series 2 models. So thank you to everyone who shared their thoughts and gave me advice back in December.
I'm very shy of dipping my toe into the debate about what a bass's neck contributes to the tone, but I'm sure I can sense the combination of the thick neck + the strings coming through the body contributing something to the ringing tone. So I'm glad I went 424 rather than 414 for that.
I can see why Yahama changed the style of the pickups from 424 to 434, can understand why the market would prefer the new ones, but for what I want the character has been diluted.
Played side by side with the skinny TRBX, the 424's neck is more challenging, but since I can (rightly or wrongly) sense what it's contributing to the glorious sound, that extra effort feels exciting, not difficult.