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.
Hooked up my new to me rkl this afternoon. So far so good. Only downside to it so far is it wont do a complicated light cycle like mine with the two on's and off's. I had to set two timers and use the multi timer function. Hope I remember to reset it after the 62nd cycle. The three on events for the t-5s is yet even more challenging. I got the temp and Ph probes calibrated and it seems to be happy. I have a second power bar but its not working at the time. Just clicks so I think its dead.