Apex and Apex lite differences?

[The Grizz]

If you just want pH & temp probes and not going to use it for anything else you could just go with the lite plus. The biggest difference I found in the RKE & RKL was the head unit. But if you get luck like I did and find a Profilux controller gently use go with it. They are all self contained and upgradeable , no extra modules & less parts & pieces.