people usually say x.x.x are like the w7's but cheaper... but if they were the same price and looked exactly the same... what ones would you buy. and if you know... which has better SQ and SPL? also which has better quality... or are they same quality? and if your willing to spend the time... why would you buy the one you picked?
For both SQ and build quality, I personally like the X.X.X.'s better. They aren't mass produced as JL is, and quality seems to be a little better. The W7 suffers from the long gap voice coil design IMO, the SQ just isn't quite as tight. The XBL^2 motor design is one of the most advanced ones out there (if not THE most advanced) SQ is a subjective matter and I can't really tell you which will sound best to you. For SPL, I'd take the X.X.X. as well.
You figure after all the marketing hype and 7 years of research JL would significantly improve the most important thing, the motor. But no, they focused on cross drilled polepieces, overroll surrounds and W-cones. It's a great sub, but I don't feel it's near the retail cost of one. I will give JL the credit of this: they actually earn their patents, unlike crappy scam companies such as Bose, who change old technology just a little and market it as their own idea with a huge team of lawyers. Bose makes some of the worst speakers out there. What I'm curious of is this: if I could secretly combine technologies of different subs hehe. Like the RE version XBL^2 motor, VC, and spider, Titanium cone from Eclipse with an overroll surround design such as JL's, cross drilled polepiece, etc. I wonder how it'd sound. Don't worry though, I'm not gonna try this and risk someone suing the crap outta me.