i'd have to agree with pirate_king that BoA and Hikki are wrong comparisons...

but in this case...i think hikki is better.. no offense to BoA fans coz a close friend of mine is a huge fan and i like her too :)

not taking into account their different styles etc... hikki is much more of a prodigy than BoA..
she wrote a record breaking sales song which remained one of the most romantic songs ever... when she was only 13 and she didn't even have a relationship LOL...
hikki can write, compose, sings, and produce her songs all on her own... she can play musical instruments as well .. piano and guitar...she speaks and writes and sings bilingual..
vocally they're both very good i have to say... but hikki's voice is truly unique... it's... very different and is nothing others could offer. they're both very beautiful and no dun worry i'm not gonna say BoA has plastic surgery... coz just like hikki... her carrer is taking place as she's growing as a teen... so obviously she's gonna change and beautify naturally right? :)
and if hikki wanted to.. i bet she coulda learned dancing as well... and that's about the only thing BoA has against her i think
plus... hikki's music genre is original and her own style in its entirety as to BoA's music which is a specifiable genre and has about a few other artists already competing with her...

so my personal conclusion is hikki's better...

and again i'm underlining that i'm not accounting the different kinda people they entertain and blah blah... i'm just saying things in like.. pure talent as a musician..u get me? .. anyways... that'll be it.. and... please don't kill me if ur a huge BoA fan i've said i like her too u noe... lol