I would stay away from the dual overflow, in my opinion they are to much of a pain to work around in the tank and can be a slight "eye sore" in a beautiful tank. The overflows that run the length of the tank at the surface are kinda neat, but they do limit some placement of things close to the surface in the rear of the tank. Depends on what you want to do with the tank and how you plan setting it up. Back to the dual overflow thing, the biggest reason i would not do the dual thing is that it gives you more plumbing to do and two sets of drains and return lines to deal with under the tank if your planning on using the under tank area for a sump. And it seems like no matter how well you originally set up a tank in this hobby you almost always have little plumbing issues at some point ( i recently just went though one of these annoying occurances). So, if you have 2 it just means you have one more area in your tank that may possibly create issues at some point. To that i would add, that i have heard people complain that when they have 2 it can be a little difficult to "tune" your water flow or drainage to the sump or with the return aspect, especially if you dont take the time to get the tank perfectly level at the start of the tank build :) But thats just my opinion...im sure there might be an advantage to having 2. I guess if somehow one got plugged the other would take up the difference. So I guess im saying what it comes down to, is what do you like the looks of more....having one bigger overflow or 2?
