<u>Return from the top...</u> If for what ever any reason you end up with a reverse siphone thru a return placed at the bottom you'll lose nearly all water in the tank during a power outage.
That being said... I have one of my tanks designed with a spraybar blowing across the bottom of the tank. You can place the return where ever you feel flow is a requirement. Just make sure that you design it in a way that will be sure to stop a siphon in the case of a return pump failure.