In the first campaign @frank.hampshire and Tony Purcell played Imperials, Imperials not having quite gelled yet. Frank I think didn’t quite get it at chargen time and would have made his character a colonial from a rich colony if he had got to do it over. Tony got Imperials very well, but I think perhaps didn’t realise that I had. Phred Smith generated a planet for his character to have come from, the egregious Thanatos (it is coming back, toned down, probably as Kemet). The other two initial players were not at all specific about where their characters were from (it shouldn’t be terribly important), but they didn’t like the campaign and dropped out after two sessions. @davidbofinger joined late, and I don’t recall his character’s place of origin being mentioned.
In the second campaign everyone played a character from the wealthy class of one of the colonies in the then-current version of Tau Ceti. Frank’s character was from Blunderbore, Tony’s from Gogmagog, Andrew’s from Odysseus, David’s from Reykjavik.
Since then, and not counting characters that I generated for others to play, I’d say that playing Imperials and being vague about origins were neck-and-neck. I’ve seen a couple of PCs from Tau Ceti — one from Hell and one from Avalon and one from Esbouvier (which is now Simanta), but none from any other world of the Suite. The few players who I recall having generated characters from colonies that I had already described mostly went for ones with really striking social values that would let them examine a very different mindset, such as Esbouvier or Nahal. And then the rest tend to ask me to help them pick out (invent) a homeworld that has some sort of social or environmental feature that they want (lots of wilderness, decaying industrial cities with street gangs, favelas and brutal police, a duelling culture, recently having been dragged out of hell by a comprehensive Imperial intervention, a military culture, a police state…).
I’m considering your suggestion of describing a small collection of WEIRD colonies at DLs that would let them approximate recent real-world values of “I” and “R”. I’m a little bit skeptical. Tau Ceti and, say, Margulis are populous, developed, and important enough that it makes sense that you meet a lot of people from there in the Demi-monde. But if somewhere small and obscure were described to serve as a homeworld for WEIRD PCs, and if it worked as such, wouldn’t it look a bit funny that so many characters were from such an obscure place?