Mecanum Auto, 2 Omni, 2 traction Auto

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We are looking for real world experience based insights or concerns re repeatable predictable precision navigating (including turns) in Auto for:

1) four 6" AM Mecanum platform, and
2) a 2 traction wheel and 2 Omni wheels platforms
versus
a standard 6 wheel system.
All will have encoders and a gyro. Are platforms 1) and or 2) equally capable of doing sub 1" precision navigating or do they give anything up compared to a 6 wheel system. Are there wear and tear considerations over a long season re repeatable accuracy ? Do they natively drive in a straight for long distances ?

Posts like ..."roller performance (Minimal axial free play and roller spinning friction) is critical to proper drive function" raise concerns to me about the wheels being able to natively track true on their own on the long term or at least requiring a lot of roller maintenance / inspection.

Also, on the topic of calculating distances traveled with Mecanum based wheels, I understand there might be a bias (different distance traveled) for the same encoder counts depending if the platform is traveling forward/reverse versus left and right. Calculating the distance traveled on angles would appear to be complicated by that.

Might as well ask, do 8" mecanums offer any advantage over 6" (other than larger radius for going over obstacles benefits)?