This is like trying to identify the world's most beautiful woman....it simply can't be done
One reason is that there are varying degrees of "custom",and the skill sets are markedly different between,say, a Jim Borden,and a Dave Norin,Duane Wiebe,Steve Heilman, etc. These skills may overlap and converge at some point, but you wind up with markedly different rifles at the end of the process.
As to "most accurate", I doubt anybody can lay claim to that any more either,at least in a hunting rifle.The techniques of getting a Rem 700 clone(even a M70 and others) to shoot lights out is pretty common today.Less common are smiths who can take a rifle and make it function perfectly,every time.
Not too long ago there was really "one" type of custom rifle and if you considered anything other than a Wiebe, Biesen,Goens etc you were headed in the wrong direction....starting in about the 80's the number of guys out there capable of that quality work proliferated;I remember attending the ACGG show in Vegas a couple of times in the 80's and was shocked at how many really top quality makers were out there.
I think this trend has continued to this day.There are many fine wood/metal/ accuracy smiths to choose from.
Just a comment on wood vs synthetics:Wood can of course vary all over the place,and I'd be the last to say that a wood stock is tougher or more durable than a good synthetic,but I have owned quite a few customs by top makers,and one of the characteristics I noticed about them is that the things never changed point of impact, nor did they stop shooting very well,even though some of them got thoroughly soaked from rain,ice,and snow, and treated pretty rough over the course of a hunt.
Point is there is a world of difference between a green factory stock,and a well cured hunk of French cut properly,laid out,bedded,and sealed by a top maker.How they do it I don't know,but I actually shot the barrel out of a 280 built on a Mauser action by Kevin Campbell,and the rifle never once required any rezero.So, just because a lot of them are pretty does not necessarily mean they are fragile to any degree,and can be completely trustworthy hunting tools.They can handle some pretty rough treatment.
