Whatever you do, avoid B10. Worst club in the system.
I'd recommend the former BizElite lounge in Concourse E for most amenities - while I haven't been in there, it's supposed to have some hot hors d'oeuvres. A Centerpoint (next to Chili's) and C Concourse Crown Rooms are my two personal favorites - very open, pretty modern, etc. Amenities at these ones are TVs, light snacks (pretzel mix, apples, etc.), free bar, etc.
Biggest CRCs are A17, A Centerpoint and E. B10 is very small and cramped (I avoid that lounge like the plague), B25 can get crowded as well.
T7 is normally pretty quiet.
Keep in mind that daypass users do not get free wi-fi - that's limited to Crown Room members only.
Also, with
DL lounges, it is not a day pass - it's a one-visit pass. If you leave the club, it's another $30 to get back in.
CO has a nice (recently renovated) lounge on Concourse D - it's either $40-45 for the pass, but slightly better snack selection and free wi-fi, plus you can re-enter the club if you want to grab a bite to eat.