I think this is a good thread for the average hobbyist who doesn't necessarily need this maybe because it's not in his or her budget but may think it's good insurance for all that money you dump in your tank and or simply because or someone who's looking to save up for a decent controller. One thing that should be seen is how much a controller is gonna cost you in the long run? Almost as much as the tank itself you know? I bought my apex lab grade used for $270 with a temp, pH probe, eb8, the brain, and the display, and it came with powerline adapters. I'm not one to be able to afford a $500-800 unit because it's not in my budget so I had no choice to go used. But I like mine. The leak detector is something I bought along with the controller new I think that is one piece of equipment that is a must have simply because it can potentially save your tank from an ato disfunction and it filling up your tank to the top, power goes out and the back siphon from the main tank to the sump starts which then you have a ups connected to your router and controller and notifies you. Yes it's good to have a controller but the idea of it being the brain of your tank is overlooked. You should be the brains of your tank regardless whether your busy or not. This piece of equipment is insurance and it can possibly fail (hoping it doesn't). As far as my 2 cents goes neptunes systems does a good job with modularity, expansion, support for different brands like ecotech marine, aqua illumination, jebao, and others and it's been in the game for a while now it's more of the standard controller you compare to any other controller. Digital aquatics reef keeper is a good controller but it doesn't have the most expandability and support for other brands. Digital aquatics archon seems promising and the fact that it's cheaper than the apex and its more comparable to the new apex and the vectra as well as GHL makes it seem like a promising contender and something I'd be interested in trying out. I will say people have told me it's easier to set up than the apex and doesn't take as much effort and research. Don't know too much about GHL but it seems like a very complex system. Maybe it's not but it's sore on the eyes for me. Ah vertex cerebral the controller that retailed for $300-400 during launch and is going to be a long time player. It seems like a quality built controller with a lot of thought. Just don't know about that big brain of its. I wish it was a smaller footprint. The other two I don't even know of. But here's the breakdown. What do you need it to do for you? What do your majority of equipment have in common? Are they the same brand. For example if you have all radions, a vectra for return pump, and vortech pumps you might as well get a reef link and you'll be able to control all those (fingers crossed ecotech marine comes out with a controller). If you want something to do stuff like ato, leak detection, pH, temp, salinity, and will always expand and always be a player in the game. The Apple of controllers then Apex all the way. I have one, I love it, can't complain, but I'm already $500 into it easy. Bought a double junction pH probe for longevity and accuracy, ALD module with leak detection, break out box and ato, temp probe, that's connected to a fan to control when that goes on and off during the summer. There's a lot to do. But l think for anyone new to this and is looking to get a controller and doesn't want to spend a lot of money up front, then get a reef keeper or Archon, or if you don't need more than 6-7 modules get the apex jr. or get a used apex. I came into the controller hype not too sure but it's nice having something to fall back on, Oh pH is too high, lower it, temps 84F fan on, leak check plumbing. It comes in handy before it's too late. But ask yourself this question. How much do you need it to do because all these test for pH, temp, out the box (except for apex jr. only temp), have power ourlefr thats can be controlled, a display, wireless connectivity, the rest you gotta figure out what you need and limit your options to find out what works for you. I'm finished lol.
The programming can at times be intimidating but a bit of persistence and the help of the Neptune community it is nothing to fear. Also the graphing function on the Apex is more robust. I especially like the compare feature which allows me to see the effects of dosing and other activities on the parameters of the tank. The ReefKeeper System Interface Device (SID) can be a bit of a problem if you keep it connected to your computer all the time. At least on my versions, if the computer goes down for any reason the system sends all of the outlets into the default mode. This can be a problem for dosers, heaters and chillers etc. if it is down for an extended period of time…like when I am away. 
