I have done both. I set up a 55 and then a 75 with a HOB
unit and when I stepped up the 100 gallon I now have, I got that tank drilled with internal overflow.
First of all, let me say, you can have a HOB
unit that never has any issues, ever. I had mine up and running for maybe 4 years, and there were a couple of issues over time. Siphon not starting up, leaks, stuff like that. Sometimes major issues like taking it apart to clean it. Remember, that thing is REALLY close to some powerful light and stuff WILL grow in those tubes, black tint or no.
My internal system has been up and running well over a year now. I guess a year and a half. NO ISSUES SO FAR.....
If I could do it all again, I would have got an internal overflow years ago, these systems are just easier to deal with. To clean my internal overflow, I just have to make sure the sump is LOW, turn the pump off, and wiggle the pipe from the bottom fitting and presto, I have the thing out and can clean it, not that it is ever all that dirty. No leaks, no mess.
It is up to you, but if you can afford the more expensive tank, go for the internal.