If you like line driving around the circuit, stick with the Evos that come with AYC and ACD, you'll be much quicker. But if you like drifting it, its easier to do so with the RS versions that come with mechanical LSD's at the rear.
I've driven a 4, a 5, a 6.5 TME and a 7, and the build quality of the 7 is way above the other earlier Evos.
I drive an Evo 4 (sometimes for work, but mostly on track-days, amateur motorsport competitions and fun-runs) and the freaking noises from the suspension is driving me nuts! Plus the entire car squeaks and rattles, not something you will appreciate coming home from work in traffic.

Good thing I have another car to use when I'm not in the mood for some serious g-forces.
The 7 has none of these NVH problems (well, not as much as the CN generation / body of Lan-Evos compared to the CP of the 7).
CAR (or was it evo magazine) said the Evo 7 is like having a proper relationship, whereas the older ones were like one-night stands. So true.
By the way, the 7's had a factory recall because there was something wrong with the clutch system, AFAIK it was the clutch master cylinder not pumping enough fluids to move the clutch, making for some harsh shifting in WOT at the redline, and the airbag was not functioning properly on earlier models. (a friend totalled his Evo 7 a few days after he got it, airbag never came out, hit a wall at 70 mph. 3 daays after, Ralli-Art HK sent them a chip for the airbag, it had to be plugged in in place of the existing one which was to be removed and the new one put in place).
Now that the 8 is coming to the US and the rest of the world (officially, not as a special parallel import), I can't wait to see how it will perform.

IMHO it looks better than the 7.