Alaska may be a better choice, as they have great partners including AA & DL (which both include priority and baggage benefits when flying them after achieving AS status), BA, Cathay, Korean, Quantas, and
others. All partners accrue Alaska elite miles as well.
Many in the FF community are speculating that the DL partnership's days are numbered, as DL is aggressively expanding into AS' Seattle hub. Of course, that would probably lead to an even stronger partnership with AA, or perhaps even a merger.
Either way, Alaska miles are far more valuable than SkyPesos.
Dan, it may be helpful to recommend on the main site for people to credit their Delta flights to Alaska, I'm sure many don't realize this option exists.