OK here is my take on these guitars.
Having bought a Korean JTV69 before the Roland guitar came out I didn't really ever test the JTV against the Roland, but after I have played the JTV69 I think I can give you a good idea of the differences.
The JTV69USA is a better made guitar than the JTV69 but not enough IMO to justify the difference in the cost. You still get a graphite nut,locking tuners and decent pickups. Medium jumbo frets and I think a 12 radius neck.
Line 6 had some issues early in production with some of the necks on the JTV69s. Mainly the high E string was slipping off the frets on the edge due to the way they had finished the frets. They have since corrected this issue. Roland got around all of this buy selling you a strat with their electronics in it,so anything you can put on a strat you can basically put on it.
The neck pocket on the JTV 69 will accept a strat neck and some players who didn't like the JTV neck have put warmoths and Mighty mite necks on. I'm sure you could fit a Carvin neck on as well . I have not personally had the high E string issue, but I have considered replacing the neck because it is a few mm thicker than a strat neck. Some people like the neck...some people don't. FWIW the neck on the USA model is the same dimensions.
You don't need an outboard box to play the JTV 69 sounds. It has both a digital hookup for the HD500,400,300 and a regular guitar jack. The JTV is made like Bapu said more for a guitarist who doesn't want to carry tons of guitars around.
Line 6 is soon to release a free "HD" upgrade to all Variax owners. They constantly upgrade their firmware and sounds. The JTV can play from its own pickups just like any guitar or it can play the JTV sounds which are awesome. You can put in a Seymour Duncan or an EMG if you don't like the way the pickups sound, but I have no problem with them.( you will void the warranty if you start tampering though) The guitar emulations are spot on and they let you modify a set of custom sounds. You can make up your own models with whatever you want. One nice thing is that if your electronics go out you still have a decent guitar to play on stage.
Remember that nice Shecter I was trying to convince myself to keep? I couldn't justify it. The Variax can rock it right out of the water when adjusted properly.
If you add the other stuff that works with the variax, like the HD series boxes and the DT series amps it is hard to go wrong with any guitar sound you can imagine.
The Roland guitar looks like a very nice setup. I have heard it played on youtube and it is also a worthy contender Since I already have a Roland synth there really isn't much of a point in me trying to get synth sounds from my guitars. Some real nerd gear heads are going both routes and adding a GR55 pickup to their variaxes....I think that's getting a little crazy but you can do that if you want.
All in all I am very happy with my JTV69. The new 89 looks to be killer for metal players as it comes with a whammy and some improvements for metal playing techniques.The 59 is like a gibson with e 241/2" neck length. It looks a little more complicated to operate with a different switch configuration...maybe someone else can comment on that.