You need a fan oscillating back and fourth and having the plants sway easy. Then you need a fan to blow out used air. In veg I use a 10$ fan and just hang it from top where it blows hot air out top hole in tent.
If you have to choose between an intake or an exhaust, I would use it as an exhaust, but allow a space for fresh air to be passively pulled in, as long as your not allowing lightleaks during flower.