Internal vs external over flows

[Tradam Yaks]

Is the main difference between internal and external overflows whether the tank is drilled on the bottom vs the side? Not including non drilled tanks with siphon overflows or otherwise. Meaning a box on the outside would be needed for a side drilled tanks therefore being external as a bottom drilled which can be plumbed into a sump directly. I suppose one could direct plumb a side drilled tank too.

If so, are there pros and cons of each aside from having plumbing, boxes, and bulkheads visible on the outside/inside of the tank? I understand having something on the outside can limit placement like being flush against a wall but more curious about performance than esthetics. I feel like having external offers more options. Like I can set up a herbie or bean animal easily.

For whatever reason im having a hard time finding these answers.

Insight into my experience. 20 years ago I had a reef tank for 3 years. 75 gal display coral tank with sump, plumbed with a 30 gal refugium, and a 29 gal tank display with other fish I didnt want in the reef. I ran a siphoned overflow and had all these tanks connected. None of the tanks were drilled.

 

[exnisstech]

Internal allows the plumbing to pass into the stand with no plumbing outside behind the stand. It's a cleaner look and will allow the tank to be placed closer to a wall. They both work the same IME. The biggest negative of an internal for me is the loss of real estate inside the tank and having to scape around the overflow. I have a peninsula with an internal but it is the entire back wall on a short end of course so I only loose about 4" of total length. On a lagoon often its dead center and sticks out. I really don't know if there is an actually difference in the amount of flow possible between the two if it were measured. I've not noticed any functional difference between them. I suppose an ext could be a possible failure points for leaks.
PS I agree that there are more options for customization on an external.

 

[Tradam Yaks]

Internal allows the plumbing to pass into the stand with no plumbing outside behind the stand. It's a cleaner look and will allow the tank to be placed closer to a wall. They both work the same IME. The biggest negative of an internal for me is the loss of real estate inside the tank and having to scape around the overflow. I have a peninsula with an internal but it is the entire back wall on a short end of course so I only loose about 4" of total length. On a lagoon often its dead center and sticks out. I really don't know if there is an actually difference in the amount of flow possible between the two if it were measured. I've not noticed any functional difference between them. I suppose an ext could be a possible failure points for leaks.
PS I agree that there are more options for customization on an external.

Thank you for the response. Clarified this for me well.

 

[mfinn]

As already stated, they pretty much act the same.
But in my last tank build I decided to go with a 2 part external overflow box with the main part on the back wall of the tank with a 3 drain pipe system.
My main reason was reclaiming space on the inside of the tank.
You do need to have the stand and tank further from the wall, but a few years ago I found one of my tanks was damaging the wall with salt spray on the sheet rock with the back filters being so close.
Maybe that was just a me thing and relative to anything, but it made me think.

 

[BigMoe]

Been debating this for my next tank. Internal is a cleaner look. But you do lose lots of real estate in the tank. I'm please with hob drains so far. May get next tank with corner drains.