Agree with Gardyloo that AA is the best overall for US based flyers.
QF is great for quickly earning status, but the burn rate is terrible. A transcon is the USA will cost 36K in econ with multipliers of 2 for biz and 3 for first.
BA is a stickler for 4 BA segments for each tier level and you lose points when moving up to the next level. Also a 2 and 3 multipler for premium class awards. BA does have one-way awards and the WT+ to CW upgrade option is good.
CX just requires a whole lot of miles and only class of service bonus miles.
AY is really geared for its own metal flyers/awards.
IB just sucks unless you live in Spain. Miles expire after 3 years, no exceptions.
JL could be okay, though I don't know much about that pgm.
LA sounds exciting until someone who is a member of LANPASS told me that they would switch to AA in a flash if it was possible (business constraints)
MA must be invited to OW emerald status even if you qualify otherwise.
RJ no knowledge