The nice thing about hot air is that its just air - this means there's no physical 'tip' nudging the part to heat it up. This is great for delicate components. Another thing is that you can heat up an entire area at once, great when you want to rework a small leadless part because the pads are underneath the chip. The annoying thing is it takes a long time to heat up a board especially if there is a ground plane involved. You can try preheating the board if you have a preheater (basically a small reflow oven works fine).
[Sources] Ladyada via ElectronicsLab, & Tequipment on Youtube
