I understand that the C Autopilot is the least likely to get knocked out by system failure.
Obvioulsy various exceptions apply.
Any sims where you are going to get electrical and hydraulic failures, the C, seems to withstand the most before dropping offline.
I think the L autopilot is next favoured, followed by the R.
I am sure others will have differing views. Some airlines alternate between A/Ps - Captains sector - use L or C, F/Os use the R.
The other thing which may impact on the decision, is transponder system usage vs Autopilot - depending on which transponder is used, it may not correspond to the altitude the autopilot is flying - ie L Transponder, comes off Capts altimiter which may be 40' diff to F/Os Altimiter - which is what the R transponder uses and the R autopilot.
Of course that depends on your airlines config too.