Woodward,

SF will beat Boulder by a mile. SF is a "company town" everybody's employed by the "company" (tech industry).

Plus, good news about SF is that these internet co's are always going out of business freeing up the talent at a good rate. Think supernova seeding the universe. So even if Boulder had more CS than SF (doubtful) they'd all be employed by big companies that have great benefits,etc.

But don't take my word for it. Advertise your job on craigslist SF and craigslist Boulder and see what comes back.