Title pretty much exaplins it. Which one is more efficient, one of those lightbulb vapes or a 15" glass bong?
Go with the bong. Glass smokes smoother and cleaner than out of a lightbulb. Plus it won't taste horrible like the LB vapes tend to do.
the bong would be way more enjoyable to smoke. but if by efficient you mean what would save weed the best i would say the light bulb vape. it takes a very small amount of good bud to get you high.