Having more exhaust fans than intake fans is likely better because you need to get rid of hot air, rather than 'recycling' it. Cool air can be forced into the casing as casings aren't fully sealed, it'll make it's way somehow.

IMHO, creating negative pressure in your casing is a good thing. You can't use this concept with a positive pressure setup as you there will be more volume of cool air, you would likely be pushing out cool air via the gaps instead.

Positioning plays an important part too. Hot air is lighter than cold air, which rises so exhaust fans should be at the top and at the back of the casing, unless you like hot air blowing beside at your face. Also, there's no point if there's an intake fan next to an exhaust fan. Be sure to check for 'air traps' in your casing as well, where 'used' air cannot escape and gets stuck due to the airflow.