I wonder...

I would definetly go with the predrilled if cost were equal and even if the cost were higher.

Why:
Predrilled units with an appropriate overflow box don't have over flow problems due to power outages or any other loss of syphon. Also if the syphon tube ever gets blocked I.E. by a snail then you will alo get an overflow from the sump getting pumped all b ack into your tank.

I agree. Pre-drilled is the way to go, even with a higher cost. The predrilled are also 'neater'--you don't have to have all the plumbing hanging off the back, and you can enclose your sump to minimize noise and evaporation and salt creep much easier.

If I get my dream tank, I'd get 2 corner overflows. Mostest definately.