ok, so i'm biased because i'm putting on the show, but i would go with nadja.
1) the velvet lounge is a better place to see a show than jammin' java. unless you love coffee and hanging out in suburban parking lots.
2) i've seen akron/family three times, and i feel that each show was regressively worse. i like them most when they play a concise/compact 45-minute set, not two-plus-hours of meandering, uninspired, sub-allman brothers jamming. and i usually like meandering jamming, just not uninspired. i was really bored after they played for an hour the last time i caught them.
3) akron/family will be around and will come through dc soon enough. nadja has never been here and doesn't tour as much.
4) aidan played my house last year and it was amazing. nadja will be even better.
5) the openers are fantastic: ami dang, from baltimore, plays sitar, and pacific before tiger does minimal ambient drone in the vein of stars of the lid/brian eno.
6) the velvet lounge needs your money more than jammin' java does :p