[As a quick digression: this kind of computation with some basic numbers is how you can quickly cut through the BS in life, pushed by everyone, to get to what's really going on: these organizations proudly market themselves as highly professional and reputable--they don't walk on the grass, able to logistically hit all the doors you need, etc. etc. without it being, really, mathematically possible.]
But for hitting numbers at doors, they're a massive difference. Rollerbaldes reduce times between houses when on concrete to a quarter or less than they would be otherwise; a Rollerblade typically has a wheel jutting out from the front which, when running, gives you an extension beyond their height and lets you run even faster than you could otherwise.
In a word, they're a blade to cut the logistical gordian knot and get to the point--knocking on a door.
That kind of realization and implementation is typically what people like to call ‘creative’ but which aren’t really “acceptable” by those who want to be “reputable.” It's also the kind of thinking you find engineers engaged in constantly--when those reputable and formal kind aren't heavy handedly interfering.