Right angle plugs put less stress on the input. Meaning it decreases the coefficient of workload on the plug itself, by increasing its moment arm. For example, say someone has injured there Right leg and they need to walk with a cane, what hand would you put the cane in order to walk effeciently? If the Right leg is injured then the cane would be in the Left hand--why because when the cane is in the Left Hand you increase the moment arm of your leg bone on the right side thus decreasing stress on the injured leg. Same as the right plug--at the moment of the right angle is the greatest of tension--NOT at the input at the edirol r-09.
for example, if you seen the show HOUSE, you know Dr. House uses a cane but he puts it in the wrong hand--notice how awkward and more energy he needs to walk around. again due to his character traits, he is defiant in doing the most obvious things in order to be beneficial.
Like a push up also, if you have your arms straight--meaning you have completed the push up--most of your weight/force pressure is on your hands ( the input of the r-09), but know bend your arms slightly know the pressure goes thru your elbows( right angle of plug) decreasing the amount of stress placed on the hands. The right angle of the plug takes the stress, making less stress at then point of the input jack.