I have actually owned a Roland JC-120 --- unlike most folks. Most people don't get all the way to the finish line because the amp sounds terrible without the chorus on - and that's true; it does sound terrible without the chorus on.
I used to play in a big funk band, and I wanted the cleanest, loudest amp in the world, so I got a Roland JC-120, and I also got a Fender Ultimate Chorus, which was kind of like getting a Camry and an Accord - two different companies' take on the same idea.
Roland JC-120:
Sterile is overused in tone discussion, so let me qualify for you a bit. This amp felt "stiff," it had a very direct tone, with 0 sag or sponginess to it. The sound that came out of it "felt" brittle. High frequencies were reproduced perfectly, and I mean perfectly --- it sounded like what you heard playing unplugged, almost as if it made your pickups a little "truer." Impossible, I know, but observable.
Mid reproduction was super "closed," like it pained the amp to do it. Mid reproduction was the thing that gave these amps the reputation for being sterile, I think. There's just something so unnatural about the mid reproduction on these amps, I can't put my finger on it too well, but the mids always sounded unnatural.
Low reproduction: there wasn't any. For a closed back 2x12, you'd expect a lot of punch and woof, but you'd be sorely mistaken - the JC-120 never thumped. Some of you know I love a big low thump in my tone, and I actually gigged for years with a subwoofer in my live rig (same band, needed big thick clean tone). The JC-120 had no low end, and you can believe that I turned every knob trying to get it there.
Fender Ultimate Chorus:
This amp sounds unnaturally warm for a solid state amp, on the clean channel. For the record, I'm only referencing the clean channel in both of my assessments. High reproduction on this amp is clear, but sweet - the speakers may be the cause of this, but the highs are not harsh, they are, well...sweet.
Mid reproduction is excellent in this amp. Fender actually added a MID BOOST button to the later revision of this amp (which is the one I had) which can really change the sound of the amp. I used the MID BOOST button a lot when switching between G-style and F-style guitars. Mid reproduction has a very lively and active feel to it --- and carries an immediacy that is generally associated with active pickups, although I never used actives with it.
Low reproduction is ridiculous --- bump city if you dial it that way, or clear and authoritative if you dial it that way.
Overall, this amp had a spongier feel to it --- almost elastic, where the amp would save up some energy and kick it out extra hard based on how you picked. It just felt alive, and the Roland didn't.
Both amps have true stereo chorus, and two separate power amps, as in the Fender, rated at 130W, has two separate 65W power amps sitting next to each other --- essentially two 1x12 65W amps sitting next to each other in one cabinet. The Roland was built the same way.
The Roland was closed back and had fixed casters, I believe, and the Fender was open back and had removable casters.
I also found the chorus on the Fender to be both more pleasing and more adjustable.
I offloaded the JC-120 to a hippie bass player who wanted it for some reason, and kept the Fender.
Real reviews based on real experience from your boy I6.