So basically most people would prefer to run the longer run in the morning, but if you have an 8am-5pm job, then you'd prefer to do the shorter run in the morning due to schedule conflicts
Anyone have any evidence if the one way is more optimal than the other.
Letsrun appears to have a particularly loose definition of "evidence." This explains a lot.
I think the natural thing would be to do the tougher workout at the time you would want to do a single workout day. Do the easy one at your "off time". I hate doing more than 4-5 miles early in the day before work, so doubles are easy morning, harder afternoon/evening.