Also, you say "it's only a 30%" difference. I gues to me, that is pretty significant considering how hard it is to burn calories in the first place. When I have to bust my ass to burn off a 250 calorie snicker bar, I want to get it done as quick as possible.
Also, the whole point of exercising isn't soley to burn calories.
Other advantages include increased respiratory functionality, increased metabolism, increased muscle performance, ect. You cannot deny that increased intensity helps improve these other important side effects of exercise as well.