In term of durability, they're both the same since they've got the same powedercoated treatment, which is WAY more durable than regular paint. Machine finished face get the clear one and other get some colors.
99% of wheels are painted, they are not powdercoated. When a wheel has a machined finish, the entire wheel is painted and then face of the wheel is turned, to machine the paint off the face. This is why you won't see wheels with machined areas that aren't flat, and aren't right on the face of the wheel.
Machined and painted are both fine for winter use as they are both clearcoated the same. However, if anything happens to the clear, the paint underneath is another layer of protection. The machined part will not rust, but salt will create white specs if it gets under the clearcoat. It's not a bad idea to apply a nice coat of wax to them before they go on each winter.