Plus I've always had a soft spot for Fukuda and Nakajima's voices so I'm probably just biased.
More on topic though, I haven't cared much for the Satoyama/Satoumi songs but Dia Lady is a damn good unit.
Fukuda is a really good singer. Her talent is spoilt on S-mileage, though (I love the group's music but the high-pitched voices stuff puts me off most of the time).
Hi-FIN sounds very good considering some of the singers involved, but it's understandable since they're harmonizing throughout the whole song. Fukuda is good already; both Ishida and Nakajima's worst qualities (an excessively forceful voice in the former's case and an extremely squeaky voice in the latter's) are overcome by their blending in with the other voices. The same could be said of Hagiwara - not a big fan of her voice type - and well, you can't hear Ikuta too much either so all's good
Mellowquad is creepy and weird but not in a funny way. Definitely the worst of the 3 songs.
And Dialady's is amazing. Love the style, love the singers, love the harmonies - yay yay and yay for Risako's alto pitch being put to great use - and love absolutely everything about the song and the video. Takui's earning more of my respect every passing day.