I'm from Seattle, so I'm biased, but Seattle is classic Shadowrun. For transparency, I know a bit about Denver and Chicago and next to nothing about Hong Kong.
Not only does Seattle have a ton of content but it also has everything you need to progress from a street-level campaign to a prime runner campaign, all without leaving town if you don't want. I had a long-running street campaign that started in Puyallup and slowly moved north as the players advanced. Puyallup, then Auburn, then Renton, then finally Bellevue. You could do something similar with Redmond too, no problem. I liked it a lot because the neighborhoods themselves became characters in the storyline. Initially the players were fish-out-of-water when they left the Barrens, but after they had been gone for a while they had to go back and have the reverse experience. ("Drek, we used to live here?") -
Seattle is fun because it's a UCAS outpost in the middle of less-than-friendly NAN lands. I always like that touch of mystery and vague foreboding just across the border. Plus, if you ever want to run a rural mission or two, then there are tons of forest and mountains and critters right in Seattle's backyard. There's also a strong Asian influence, so it's easy to include anything from the Pacific Rim. Vory, Triads, Yakuza, Seoulpa Rings, Japancorps, you name it. Have them cut their teeth with street gangs, then move on to organized crime, then end up as professional runners striking the corps.
Denver is tricky because you have so many borders to deal with. Maybe you handwave those as a GM but they can be a big logistical hurdle than you may or may not find to be fun. On the flip side, Denver is primo for smugglers if you have players that want to play riggers and/or mess with vehicles.
One of the neat things about Denver is you get a lot of different players in a small space. Want to run something with the Wildcats (presumably once you're prime runners)? Hop over the Sioux sector and have fun. It also has a lot of nearby wilderness, like Seattle. Ghostwalker can be the Prime Mover in the background, if you like major behind-the-scenes actors.