A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
Sometimes there is enhanced availability if you are using miles or especially are an elite in the FF program of the airline you wish to fly.
Currently DL miles don't expire, so that might be a consideration in their favor, but DL award availability is generally regarded as not being very good, especially for business class tickets.