Hi, quite a lot of people actually use this system, many more so on plant specific forums as most people on here tend to go for liquid carbon or DIY kits.
The only problem i have had is with the connection between the bubble counter & regulator. It was leaking but it is a quick & simple fix by usig some PTFE tape around the joint which sealed it up perfect
The first one is the most commonly used, but there is nothing wrong with the second one either.