Performance of the G1 is exactly what we would expect from a high-quality single coil deck, i.e., wonderful. Sure, the TF-RTA can produce monster clouds from either the G2 or G4 decks, but the G1 deck gives the user the additional option of vaping the tank with the simplicity of a single coil.
Not that the G1 is a slouch at vapor production. With the pre-installed Clapton coil, you can still blow big clouds. What the G1 is for, however, is lower-power flavor chasing. I used my TF-RTA with the G1 deck at 35 watts and was completely satisfied.