Stainless is definitely harder to braze. I used stainless frame parts
starting with Art Stump dropouts in '77; I even made a few all-stainless
frames, including the one pictured at
http://bulgier.net/
I always had to clean much more thoroughly, and heat much more carefully, to get as nice a result in stainless as I could get effortlessly in most other steels. I still like stainless though, and wish I had made one for myself - never got around to it.
The dull finish on the frame in the link above is a quick'n'dirty scuffing with ScotchBrite(tm), because the customer was on a budget and polishing the whole thing would have been expensive.
The cool way to make an all-polished frame is to polish the tubes, lugs etc first, then braze it clean and leave it. The birth trauma of the framebuilding process inevitably leaves some scratches which need to be polished out, but still you can't beat that look of a tube that's polished right up to and even under the lugs and braze-ons. Definitely just for rich guys though - too finicky for a practical rider.
Mark Bulgier
Seattle, Wa
USA