I also use an RKL, mainly because of price (I purchase most of these things in the used forum). I have heard great things about the Apex. The only thing I wish I had was an ability to control the vortech pumps, but can certainly live without that.
The better way to answer your question is if you let us know what all you actually want to control. Apex is the most broad spectrum in terms of controlability, but the reefkeeper isn't far behind IMO - if you don't need specific controls for something like vortechs, the cheaper deal may be the reefkeeper.