Western music, no contest.
Sometimes I feel like a lot of Jap music post 80s is more unique and impressive than Western equivalents - probably just cause I'm a big weeaboo, but they do have a way of coming up with new spins on something. Like Japanese new wave I sometimes feel like the songs are more energetic, well written, melodic than over here, or with VK I feel it's better than the scene/emo bollocks going on today or your typical poncy hair/glam metal. Even the really mainstream pop I feel is better than American pop - sugar high techno driven, anime style pop music probably grates on a lot of people's patience, but I like it and have no shame. Don't care if that makes me gay. Also, like the guy above said, Japanese-influenced Western music is normally a good idea. Never heard Yoshida Brothers though (sounds like I'd like them), but a lot of J-pop and artists like Ryuichi Sakamoto and YMO have Japanese melodic scale.
Still the fact remains that these people are aping Western sounds and that ultimately, without Western music Japan would still be playing shamisens and shit. Well that's daft but you know what I mean. They're better at taking certain genres we've done and going at it with more enthusiasm.