Both types of membership let you earn points on flights and shopping (shopBIG), redeem free flights and hotel packages. For the BIG Visa Prepaid, you just need to pay RM 10 for one time joining fee, then you will be entitled to earn BIG Points (RM 2 = 1 BIG Point) whenever you spend at any VISA accepted merchants worldwide and BIG Partners. Besides, there is no processing fee imposed if you pay your AirAsia booking with BIG Visa Prepaid.
You can also convert your loyalty points from participating partners to BIG Points in order to fly for free. Redemptions are available at a mere start from 100 BIG Points.
Occasionally there is also exclusive promotion for BIG Shots (BIG members) to redeem air tickets, as shown on the picture above. If you like travelling, I would recommend you to sign up as a BIG Shot ASAP if you've not done so.