The NRG is good for big jumps, long floatr and upwind ability but is slower turning than the Envy.
IMO the Envy is a much more versatile kite and it fun on lots of different boards. If you like the Envy in the 12m you will love the 9m and the 7m, this 3 kite combo will get you going in light winds on a surfboard and even strong winds on a surfboard or TT.
i rode the 2013 NRG, anything bigger than a 10 is not fast enough for a surfboard. Its a kite that is best suited to a twin tip, if big jumps is what you want then the NRG is perfect. but having said that the Envy can jump fairly well too!
I rode my 9m envy in 35 knots a few times at 145 lbs/65kg and it is fine, not ideal. If you dont have those 30 knot days often I'd probably go for the new sizing, 15 and 10.5 envy and if you need more top end there's an 8 now.
ok i rode all LF2013 kite models already. the NRG 2012 was a great lightwindkite, but the barfeeling and the relunch was not on the same level of other LF kites. now as i the reviews before stated, it has everything a kite should have. last years NRG was a lighwind machine and probably a good racingkite (i don't know i don't do racing). the 2013 is just a fast, direct, hangtimemonster, fun kite with great lowend and control. it unhooks still decently but it will never stop pulling. so if you want more freestyleoriented kites look for the envy or even the hifix. i tried 10,12 and 14 and i am so much looking forward to try the 16. they all have great lowend and in their upper windrange the lift and the hangtime are insane.
what other models should the nrg be compared to? probably a north rebel, a cabrinha switchblade or crossbow or something in this category. i havent tried those kites recently but thats probably what it should be compared to...