one thing for sure - G system has NO drrives. unless u have a good amp with good drive, or single stompboxes to compliment the G system, go for the nova system
nova system is like the 3xlive, or the m13.
G sytem is like the x3live WITHOUT the drives (their logic is - drives would be bought by hardcore guitarists to suit their playing whilst the other stuff i.e. mod, delay, fx, would be 'general')