Def external. Years ago I had internal and I hated that it took up so much space and was not appealing. Here it is getting filled and more space for rockwork and corals. My current one is external and it’s very clean look. You can also design creative DIY to hide the overflow box also if that’s not appealing.
So I'm still deciding on which tank to get for my upgrade. It'll be a 6' peninsula. I'm pretty decided on it being a 72"x30"x24" tank. I'm planning to go with eurobracing.
...but this brings me to my next question for you guys... which do you prefer: internal overflows or external overflows and why? I'm currently leaning toward an external overflow.