The 6m is the only Rage I've flown.
However, I've flown it back to back with my 7m Blurr and 8.5m Blade IV. The Blurr is the slowest so the poorest for light winds. The Blade can only really be bettered by something like a 15m Flysurfer Speed 3 Deluxe (I've only flown the quite frankly awesome Speed 3 back to back with my Blade), but as I don't own one, when it gets really, really light, and the Blade gets hard work constantly looping such a big kite, I've found that the Rage 6m surprisingly slightly better.
Obviously I've noticed the wind window getting smaller as the wind gets lighter, but I have to say I have never notice that it feels smaller flying my 6m Rage compared to flying my Blade. You have got me intrigued, the next opportunity I'll make a comparison.