I tried out the REV 2 down in OBX and loved the kite. I didn't get a chance to try out the RPM. I understand the shape difference but I am not clear on how that effects the the performance. Does the RPM fly a little deeper in the wind window or does it fly closer to the edge of the window? Do they relaunch the same? Everyone says that the RPM is better for unhooked riding so I will take your word on that as I haven't progressed that far yet but plan to. Which kite is faster? I kite the great lakes and have to deal with gusty conditions quite often. Is one kite more stable than the other it gusty conditions? I plan to demo the RPM but even during a demo you don't get to experience all of the conditions that you will encounter over time and I need a kite that is very versitle in all kinds of conditions.
RPM in La Ventana- http://www.vimeo.com/3085705
Here is a good link that showcases the RPM in real world conditions.
I think the RPM is a bit quicker and fly's closer to the edge of the window but with regards to steering that all depends on how much bar input you put into the bar. The REV needs very little to start a turn where as the RPM needs just a little bit more. But the setting on the RPM does allow you to increase or decease the amount of input you need and bar pressure. So easy tuning is great to get the kite dialed to your riding style. With that the RPM is much easier to pass the bar because of this; i.e. it is not as twitchy with bar input as you pass.
The REV will relaunch the best out of the two but the RPM does have a pocket in the wing tips to allow you to have the easy relaunch of the REV. Add that and its light weight, it will relaunch in even the lightest winds; if not be able to reverse launch for you if the standard method does not work..
Winter relaunch video- http://www.vimeo.com/3366482
The great thing about the RPM is that it almost has two types of depower. First with the throw of the bar and its shut off; And second with the rider being able to stomp the kite and edge into the wind window to depower it. Seems like a long lost technique but C kites where very good at stomping and this is some of the characteristics you will get from the RPM. Also when pumped up to a good psi the kite will be almost as stable as a 5 line C kite... The bridle and the over all design of the kite really does a great job at handling gusts and very inconstant winds..... and I know the Midwest is know for that...
If you live in the Twin City's area stop by Midwest Mountaineering and ask for Peter Noren. They have RPM's and should be able to answer your questions and maybe even hook you up with a demo. Just tell them shy sent you.