Brooklyn reminds me a lot of Boston, tech-scene wise. There's a plenty of computer programmers around and a fair number of of young entrepreneurs, not to mention a startups located there. I know a few bars frequented by coders and there are coffeeshops galore. Not having spent time in SF I'd still say it's probably a more arts/entertainment oriented than tech oriented crowd, but the recently gentrified areas of Brooklyn are lightyears away from old-money Manhattan.