My review will apply to either the English or Korean version - doesn't matter because I don't consider lyrics.
Personally I don't like the song - why would I listen to a Korean girl group trying to sound like they're Motown from the 50's or 60's when I know and grew up listening to (I'm not that old though!) the real thing? It's rather stupid. But I could say that about every other genre so I'll keep my mouth shut now.
Their vocals are strong and there are really good singers in the band, but I tend to not notice vocals that much anymore when they're mostly strong - they've reached that level of musicality, I have to look higher and by that I mean to the music itself and how they grow as artists/musicians.
The instrumental isn't anything to rave about, it is what it is, and the vocals are strong but not breath-taking. 2 Different Tears is very 60's ish by nature, the video is as well, and to be honest I can't find any other way to describe it except that it really sounds like The Wonder Girls, I can't imagine any other existing Korean girl group actually pulling this off. That's for most of it a very good thing.
The one good thing about what JYP does to most of his acts is that he makes/lets them grow musically - they debut with a sound and branch off from that but keep a quality/qualities of that first sound. The entire point of having a mentor is for him/her to steer an artist to a direction that fits them and help them grow into their own artist while learning tools of the trade - mentors have been through what their "disciples" are going through now, or at least they're supposed to, which is why I personally think out of the 3 big companies that JYP and YG are very good mentors, because unlike LSM who's business business business (even if he sucks at that part too), the founders of YG and JYP were actual pop stars once upon a time and they know what being a star means.
But back to the Wonder Girls. If you listen to Irony and you listen to this new song, you wouldn't think there are any similarities, but you listen to everything between the two songs and you take them into context there has been a growth in their music.
Their members might've changed and they might've promoted the same song for 2 years, which really pisses me off, but their material is consistent and they've created a niche for themselves in Korea. In the US not so much, but they're definitely one of the few major girl groups, if not the only, who do this kind of music and you gotta hand it to them for knowing exactly who they are or who they're supposed to be as a band - they're the prime example of how kpop girl groups of their generation can actually put out cohesive and well-produced pop material.
I think I strayed off a bit. Point is, I don't personally like 2 Different Tears but this is the very manifestation of who they are and how they've really perfected their craft - that's pretty much all I actually ask for in a pop band. Of course me actually liking the songs is great too but I can settle for material like this.