my favorite song is "Zukkoke Otokomichi".
i think they're doing fun/cracky songs as their main singles because it sells and its an image that works well for them, like how KAT-TUN's all "tough" or whatever, lol. but i enjoy their band tunes more like "Rolling Coaster". i think they were marketed as an enka-influenced group at first because i don't think they were meant to debut nationwide. Osaka is a very festival/traditional/arts part of Japan. their early music reflects that. and by early music, just "Kansha ni Eight". (& even that album wasn't even strictly traditionally Japanese too. there's a lot of pop influence.)
because they have only a few enka-influenced songs if you look at it...pretty much just Naniwa Iroha Bushi, Sakura Enka (Oh!ENKA), Mugendai, etc. to name a few.