I've never been to the Swan or Dolphin, but if I find out they have honest to God lap pools (and not mini ones), I'll stay there.
Disney pools aren't designed for lap swims. If you want to go super early in the morning or late at night (when other people aren't there), you can use the main pools to do some swimming, but they're still recreational pools. I think my favorites were Grand Floridian and Boardwalk. AKL and CSR weren't too bad, IIRC. Beach Club is the worst of the bunch.
If you plan on early swims, you'll be swimming with ducks more often than not. I kind of enjoy that, but it creeps a lot of folks out.
IMO, a good swim with the ducks is the best way to begin any Disney day.
Good luck!