Couple of comments...
1. I have a fair amount of different bolt action rifles. My TL3's and Defiance actions certainly feel nice, and bolt manipulation is very smooth. However they sometimes can be temperamental. When I ask people what they are looking for in a rifle, I tell them they can go two ways - a. build it yourself, and you are the systems QC engineer, or buy a Factory rifle, where the factory has tested the complete platform for QC. The benefit of an AI (any factory rifle) is that the factory is on the hook to validate the entire platform. Some companies do a better job than others, and that is what you pay for when purchasing a factory rifle. A comparison of a custom built rifle and a factory rifle are not apples to apples in my opinion. More like making a weighted decision - like how much error can you accept based on what your task is.
2. One of the reasons I purchased an AI is the proof testing. European manufacturers are required to proof test every firearm. There is no such requirement here in the USA, so manufactures can do whatever testing they feel is warranted. This may be 1/1000 unit testing, or simply a design test. So when I was concerned about the safety of an action, I wanted to know what level of testing was performed by the action manufacturer. Because the new AT-XC has better safety features, I will likely upgrade at some point. I don't think the AT-X is an inferior action, but I like the additional safety features added to the AT-XC
3. Bonding - one of the reasons I was interested in a bonded action isn't the fit of the action to the chassis per-se but instead to resist dust infiltration into the mechanics of the system. However I wonder (hope) the new AT-XC is easier to disassemble and clean. Also, after having a failure in my custom TL3 where the action bolts came loose on me during a 2 day competition, I was hoping for a backup to the action bolts coming loose. Currently in my custom actions, I check bolt torque after every day in a 2 day match, since that is often a problem for custom bolt action rifles in a 3rd party chassis. I am hoping that the AI will not have this problem, but since it is more like a custom action I will likely check them anyway.