Hammer forged is used by the large manufacturers because it is an economical way to turn out a LOT of barrels. It is not economical for small manufacturers, thus you will rarely (if ever) see custom barrels done with that method. Doesn't mean it won't work as there are many accurate hammer-forged barrels.
Button rifling doesn't require the same number of barrels to pay for the machinery and you will sometimes see custom rifle barrels made that way. Douglas, for many years, advertised how smooth their button-rifled barrels were as a selling point. Remington invented the process but I don't know if they have switched to hammer forging or not. Marlin did button rifling with the Micro-Groove barrels, I think. Not sure what they do now. Ruger is forging barrels, I believe. Winchester went to hammer forging as part of the post-64 changes. Although the push-feed model 70s were maligned for the overall changes, the barrels were probably better than the previous cut rifling.
You can sometimes tell what method was used. If there are radial lines in the grooves, then it was forged or button-rifled (and probably a little rough when it went through the process).
There is EDM and I think that Smith & Wesson did that for some handgun barrels but I do not know if it is commonly done for rifle barrels. In theory that would be the smoothest of all, depending on the machinery setup, rate of production, etc.
Suspect the majority of the bench-rest rifles have either cut rifling or button rifling, because they come from very small scale manufacturers and get made a few at a time.
If you want an informed opinion, call Shilen, Pak-Nor, Krieger, etc. Be prepared for them to tell you THEIR method is best and the rest of the crowd doesn't know beans
I doubt highly you can get a definitive, provable, non-controversial, absolute answer. I'd speculate that whatever method drills the straightest, smoothest hole through the barrel at the start of the process is going to end up with the "best" barrel at the end of the process. One thing's for sure, if they aren't stress-relieved before contouring, then there may be issues with bores opening up a the muzzle end with the forged/button-rifled barrels.