Both? LOL
When I get ready for a show, I gradually decrease calories (Usually by decreasing carbs), and gradually increase cardio!
This debate has been going on forever, and I have yet to find a clear answer....
The book Sliced by Bill Reynolds and Negrita Jayde discusses the importance of focusing on keeping calories as high as you can and increasing cardio. But my old prep coach, Sean Sullivan (IFPA Natural Pro) would preach the opposite emphasizing the importance of keeping cardio as low as you possibly can and tinkering with the reduction of calories.
Personally, I would rather eat less and do less cardio, than eat more and do more cardio! But when prepping for a show, it never goes how you want it hahaah I always end up eating less and doing more cardio LOL
Good Luck!