I will have one in a few weeks. I have 4 tank sharing a common sump. 2 tanks are drilled in the bottom of the overflow area and two are drilled in the back. Had to do it this was because they will be stacked and the lower tanks will actually sit 6" lower then the top of the sump (In adjacent room) so I had to drill the backs to keep the flow from being restricted by the up force of the sump being taller.
Anyways, from what I know and have confirmed with a plumber who helped me out a little is that it won't matter where the drains are (Bottom or side) as long as they are below the water line they will flow the same. (Providing I don't use a 90 right after the bulkhead and another 90 on the bottom of the first run down)
So both bottom and side will drain down into a 45 then towards the sump and into another 45 which is much smoother than 2 90s.