There are good reasons why someone might choose Cali or Dutch over UK bud, but I think the rationale behind it has been somewhat drowned up by hype/fashion. But ultimately, Cali or Dutch bud should - in theory - come from more accountable growers. 'Real Cali' is tested, and it's quality verified - that will be appealing to people whose 'street' purchases might be questionable. Same goes for Dutch, to a degree. In as much as if this is sold in a coffee shop, it has to compete with all bud in all coffee shops, and is therefore expected to be of higher quality.
There are also legacy reasons, possibly. Pre-legalisation, I used to get bud in from Cali - I've long believed the best outdoor grows come from that region, and I like outdoor grows! But the geography of the 'Golden Triangle' in Cali does offer the ideal growing environment - but with modern genetics close to hand (unlike more traditional growing regions). The sheer number of smokers/growers there also led to the early(ish) medical legalisation there, which also helped the scene. California deserves its reputation as the home of amazing cannabis - but certainly not everything from there is great these days (I suspect the black market here is largely their rejects!). Similarly, Amsterdam's been the home of modern genetics on this side of the ocean, with the coffeeshop scene encouraging at least a base level of quality.
UK bud doesn't have that same provenance. There are some famous cuts, sure - Exodus, Blues etc. But nothing else that implies any guarantee of quality. But, of course, with the same seeds and equipment, there's no reason UK bud couldn't theoretically compete with the best. Indeed, nearly all the best buds I've ever had have been UK grown. I'd never specifically choose Dutch over UK and I actively avoid marketed Cali in the UK (it's either fake, reject or over-priced!).
The one origin label that does prick my ears up is Canada. I believe their gear has a lot of the same advantages, but isn't exploited in the same way. If I want cheap, reliable quality, Canadian vendors top the charts. But for pristine high end, I stick with good growers of nice genetics in the UK.
