I've found that best usually isn't most economical so they are not synonymous. Also both terms are rather subjective and what is best and/or most economical to one person is probably entirely different to another. That said, I'd probably put in fiberglass insulation with kraft paper facing for a vapor barrier. I know there are some places in the south such as florida and south texas where the vapor barrier is put on the outside. Check with your local building inspector, building contractors, and hvac companies to see what they do in your particular area. Use a non expanding foam insulation for the cracks around window and door frames.