I'm gonna say too that it depends.
For the mini L I have set up right now, I built a relatively large custom stand to accommodate a 20lb CO2 tank and a sump, making it about 3' tall. That also puts it about eye level for me when sitting at my desk, which is nice.
When my 29g was up, I had it on a standard 30" stand, which was about perfect for the tank height and viewing from my bed and across a room, without the light being high enough to get in most anybody's eyes.