Re: For those who have a CZ 452 Varmint?
The barrel lug can affect accuracy, either possitively or negatively, dependent on its torque value relative to the action screw. However, I wouldn't consider it hugely significant.
In deciding between the 452 or 455 the principle question you need to answer for yourself is:
1. Do I want tha ability to have a multi-caliber rifle or will I desire to add an aftermarket barrel to maximize the accuracy potential of the rifle
If the answer is either "yes" or "maybe" then you will need to purchase a 455. If the answer is a solid "no" then a 452 should be your choice.
The only significant difference between the two models (accuracy wise) is the 455's ability to easily replace the factory barrel with a high end custom aftermarket barrel. Both models are pretty accurate rifles but the 455 with an aftermarket barrel starts getting closer to an Anschutz level of accuracy.