The Rxton 9 is factory boosted IIRC. Very high tack levels and a very fast rubber -- it's spin & grip remind me a little bit of a Xiom Tau 2.
The Rxton 7 however isn't factory boosted so it's a bit slower, but apparently you can buy a booster from Xiom Loki specifically made for it. One of my Chinese buddies says the R7 is quite popular in China but is usually boosted.
Without booster the R7 is slightly less tacky than the R9, but naturally has LOTS more dwell time to its top sheet -- It kind of feels a bit like a hurricane 2 to me in that regard.
Personally I love the R9 over the R7 for my FH looping game, but greatly prefer the R7 when it comes to serving. (The dwell time & spin you can get serving with the R7 is downright diabolical! 😈😈😈 I just bloody luuurrrrrve serving with that puppy!!