Do not search for a global "best version." It doesn't exist. Follow this 3-step decision tree:
What is your IT policy?
What is your risk tolerance?
| Your controller | Recommended version | Alternative | |-----------------------------------|----------------------------------|-----------------------| | ControlLogix L55 / L6x | RSLogix 5000 V20.06 | None (V21+ won’t work)| | ControlLogix L7x (no new safety) | Studio 5000 V28–V31 | V20.06 for stability | | ControlLogix L8x / CompactLogix 5370/5380 | Studio 5000 V32–V35 | V35 preferred | | Any safety controller (CIP Safety) | V28+ (V32+ strongly better) | Avoid V21/V24 | rslogix 5000 version better
The argument for "better" versions centers on three technical breakthroughs introduced in the transition to Version 21 and beyond. Do not search for a global "best version