I'm exactly evaluating those 2 options...but recently added Panama as another alternative because the economy there and way of life are very good.
I began a thread a couple of days ago on this same topic (I post both in English and Spanish) and so far Costa Rica seems safer but expats are causing too many troubles to locals. And Colombia seems more vibrant and active but locals are telling me to watch out for overpriced services to tourists and certain security issues.