I have a RKL and am very happy with it. I just use it for mainly my lights, couple fans, an air pump, and the temp probe. Considering the cost and my purpose, it's great. If you should want more capabilities then look into the Apex. Im not saying the Reef Keeper is not capable of more features because it is but when cost and purpose is the main factors, I chose the RKL.
Break down what you would want to do with the controller and go from there.