The results are in!
S/mileage first week sales:Onaji jikyuu de blahblah - 17,998 (4 editions)
Ganbaranakutemo - 18,987 (4 editions)
Koi ni booing buu - 19,049 (5 editions)
Samui ne - 19,309 (5 editions)
Choto mate kudasai - 19,700 (5 editions)
Dot Bikini - 20,043 (5 editions)
Yumemiru fifteen - 20,438 (debut single, 3 editions)
Short cut - 20,492 (5 editions)
Tabidachi no haru ga kita - 22,560 (5 editions)
Tachiagirl - 22,792 (2nd gen debut single, 6 editions)
Suki yo, junjou hankouki - 22,866 (5 editions)
Atarashii watashi ni nare - 26,753 (5 editions)Uchouten love - 29,328 (grad single, 5 editions)
Please miniskirt postwoman - 34,132 (grad single, 5 editions)
Just a list I threw together comparing all of their major singles, the number of editions they were released in, and any associated "major events" that could impact the sales. Atarashii is their top selling "non-event" single and their current top selling single since 2nd gen was introduced.