I've noticed something interesting in my comp.
I've tested both ways and determined that sucking from the CPU was the best method for the following setup: two fans in the back, both the same strength as the CPU fan. Sucking from the CPU delivered 5 or more degrees cooler. But when I removed one of the fans in the back, the temperatures skyrocketed. So, I tested the blowing method and it worked cooler by 5 or more degrees.
I conclude that when you have 2 times the air being sucked out of the case, not including PSU, sucking is the best method. However, when you have less than that, assuming it will be just 1fan of equal strength to that of the CPU fan, blowing is the best method.