Now should I go with the Contender or Encore frame?
The Contender is more compact, can take rimfire barrels without modification, and (so I've heard) has a better trigger, although admittedly that doesn't say much when comparing it to factory Encore triggers. The only downside is it's a weaker action, so you have to choose use lower pressure cartridges unless its the 223 case head size. The 30-30 is about the limit for bottlenecks, and the 44 Magnum is the limit for traditional handgun cartridges.
The Encore is beefier and stronger, and will allow you to run virtually any cartridge you want: the 308 family, the 30-06 family, many belted magnums, and big bore revolver cartridges like the 454, 460, 480, 475, and 500.
Both will handle the 300 Blackout just fine.
Great information! I'm glad I stopped lurking and signed up. 14 inch contender barrel in 300 BO it is. Does anybody know if either the blued and walnut or stainless and synthetic offers something the other doesn't? Is there a reason to pick one over the other? I personally like the looks of the blued and walnut.
A Contender with a 14" 300 Blackout barrel sounds like it'll be a great choice. I would suggest getting it threaded for a suppressor, but . . . Illinois.
I don't think there will be any downsides to choosing blued or stainless over one another, or walnut vs. polymer furniture. If you had a heavier recoiling cartridge picked, I would suggest a Pachmayr grip and forend to make shooting it a bit more comfortable on your hands, but I can't imagine a Blackout Contender recoiling that bad. It's hard to beat the looks of walnut on a polished blued gun, too.
There's also a third option: custom laminate. I've done an Encore build with a HausOfArms grip/forend set that I think turned out pretty neat:
