Don't get a G pen, they're not durable by any means, after a month or so of heavy use, mine was mangled, and wouldn't fit together right, and I eventually ended up yanking the wiring out of it from removing the tank from the charging port.
I'd say go with an Atmos RX, it keeps the taste, and they're rugged as fuck, the only thing you have to worry about is pocket pressing the power button and burning your leg. But as long you keep it in two pieces when you aren't using it, that won't be a problem.