If there only the one raised tube putting it at the back offers the benefit of setting something on it without it sliding off before you lash it down. It would also give some support and security for any payload against mounting G-forces if/when doing spirited launches.
The only down side if you can call it that might be that maybe it looks more "normal" with the high tube in the front. You might also run into an instance where the high tube in the back prevents you from carrying something larger that would otherwise cramp your pillion's style.
I'm lazy and might just want to set something (helmet or jacket) on the rack for a few minutes or hours while the bike is parked. Unless the rack is pretty level having the high tube in back would be my choice.
The only down side if you can call it that might be that maybe it looks more "normal" with the high tube in the front. You might also run into an instance where the high tube in the back prevents you from carrying something larger that would otherwise cramp your pillion's style.
I'm lazy and might just want to set something (helmet or jacket) on the rack for a few minutes or hours while the bike is parked. Unless the rack is pretty level having the high tube in back would be my choice.