The one on the right was the first and was published by Hasegawa on his own blog. We think this looks a lot like a book cover and whilst we like it's simplicity we're not sure it makes for a very good "boxing" poster". The other poster, released more recently, has a really exciting look to it, like a movie poster. We'll admit we like the one on the left more as a boxing poster.
(Image courtesy of http://www.sansei-rd.com and http://ameblo.jp/hozumi1216)