"... they have different community structures ..." That's the kind of thing I usually put emphasis on. Technical decisions are usually social decisions in disguise. Look around for local users groups, attend a few meetings, and see what kind of folks have been attracted to the languages, and see who you want to hang out with. You might also look at what different companies you're interested in are using, but there's limits to that reasoning (e.g. Google hires some really good perl programmers, they just don't let 'em program in perl.).