The main difference from the Novo is the massive improvement in battery capacity, going from the original 450mAh the Novo 2 comes with almost double that at 800mAh. Double the battery capacity means double the battery life.
Power output has also increased from 10-16W to 6-25W giving you a wider wattage range. SMOK also redesigned the draw activation sensor so it never fires when it shouldn't.
The NOVO 2 takes Novo 2 pods as well as the regular Novo pods!