I have exchange several e-mails with Todd Bettin (Bettin Custom Guns) about building me a rifle. I was up front and asked him about the differences in the ABS Barrel vs. the Christensen arms carbon wrapped barrels. I realize he is trying to sell his product/service, but he gave me pretty much the same answers that your have read on this forum. Christensen's do not shoot consistently.
There is also a difference in the way they wrap and the materials used. There are some articles out there which tell you about these differences. I believe it was in "Popular Science" magazine that there was an article about the process as well.
There are several other custom rifle
builders that use the ABS method (Jense, MPI). I am sure any of them will give you the same story. It is actually quite interesting to read for yourself. For instance, carbon fiber actually holds heat and shrinks when heated. I guess you can imagine what that does to accuracy. ABS system eliminates this inherent property of the carbon fiber. There are also different qualities of carbon fiber as well.
I have not talked to anyone at Christensen, but the builders that I have talked to about the ABS method are very open about their method and materials. used.
They are more expensive, but you pay for what you get. Bettin guarantees 0.5 or less with his rifles. He is very accessable and willing to answer your questions.