Drilled or External Overflow?

[lastlight]

Even if both are considered reliable I'd choose an external (not HOB) overflow anyday. No holes drilled in the tank itself and it's strictly gravity without any reliance on a siphon. Even if both are safe I'd choose the external. Better with resale too since 99% of reefers would prefer a true overflow as opposed to a tank that's not 'reef-ready'.