I've had a bunch of the Pac-Nor polygonal barrels, ~ 10. Many shot extremely well and most shot exceptional (as installed in custom "clened up action" rifles. One was a turd and I had to replace it, it was a 223 that would not group to smaller than about 1.5MOA. Before I had that barrel replaced I had it borescoped and it was unbelievable how many obvious anomalies there were. In one spot it looked like it had been gouged (de-laminated type look), there were "hard spots with the trailing comets" and generally a mess. I'll see if I can find the section and maybe get a picture or two.
On the good shooting polygonal barrels I several times tried to get them to shoot monolithic bullets (Barnes & Lost River (the Lost River attempt was on a special deal with Warren Jensen to test polygonal)) but these solid, non-copper-jacket lead would not shoot very well at all and the pressures went high pretty quick even with listed minimum loads.
I've had Schneider polygonal too but based on the Pac-Nors I didn't try Barnes in it.
I'd say I've had better than 30 custom rifles built of all types and I now no longer use polygonal.
I'd go with a quality 5R type or high end conventional that's been hand-lapped by the barrel-smith.