I've ran a CA RX before the current dosing system and it was a lot more headache and heartache than the dosing system. First of all, your PH is always low unless you do something about it(using airstone, pull outside air into skimmer). Secondly, there's too components that can fail. The CO2 tank itself is pretty dangerous but people don't tend to think about it. The regulator(unless you spend $$$$ on a electronic one) always need to be adjust or replaced. The check valve also need to be looked at frequently. The bubble counter can leak over time, and the needle valve that control the effluent can get clogged. The media inside the chamber is basically dead stony corals. They contain a lot of phosphate.You'll have to keep this in mind and take the necessary step to remove it.
With a tank that size, I would try a dosing system first. If it's not sufficient for what you're keeping, you can always add a CA RX.