I started playing tennis with an rd-7 when a friend of mine gave me his spare for 40 bucks. From ther I moved on the rdx 500 mid. I loved it, but I have recently switched to the Tour 10 VE mid. IMO it's more solid of a stick. They play similar but with the Volkl I felt more control and it's a lot easier to handle. You can really drive the ball. With the rdx, I didn't have the same stability nor control as I do with the VE. It feels too flexible and unstable at times particularly at the net. However, the rdx had a lot more spin potential on kick serves and lops. Overall, I have decided to switch to the Volkl Tour 10 VE permenantly. It's a scapel compares to the rdx mid. Last week, I was on fire with it.
I also use a Prince Diablo Mid. Great frame (spin, power, and control), but it feels too stiff for me right now. Maybe I can string it with a soft multifilament. The Volkl, IMO has right amount of feedback and most importantly it manuevers best out of the three.