The DL ones are less expensive than the WDW ones.
If you want to do a resort photo session you can also have those pics added to your Photopass account for $70. You get the 30 minute session, some prints, and a CD of all of your session photos, then you can add those photos to your pre-ordered CD so you can do graphics and whatever.
The PhotoPass people in the parks are just people - they have no formal photography experience. The quality is HUGELY variable. Ours have been off center, overexposed, blurry, you name it. Your best bet is to get as many pics as humanly possible so you get your money's worth out of the decent shots.
Speaking of resort photos, I am still wrestling with wardrobing.

So I would suggest thinking about outfits NOW if you want to do resort photos.