inverter: people tend to choose this when they only have an AC adapter and don't want to spend lots of money.
carnetix: the popular one outputs the 19V common for laptops (and, thus, same function as an auto/air adapter), but has additional features: SDC, and 12V for a 7" LCD.
- If you won't use an external LCD, then you don't need the carnetix to power it.
- If you already own the auto/air adapter, then you only need a 12v converter or just plug it directly into the cig socket if you're brave enough.
- If you *don't* already own the auto/air adapter *and* will need a 12v converter for an LCD screen, then getting a carnetix just makes it easier because it's 19V, 12V, and SDC all together.