You dont earn points and SC on flights purchased with points generally.
Really its your choice, In aus the 2 main choices are Qantas or virgin. Qantas have high taxes compared with virgin, but offer more routes and options wiht Oneworld. Virgin lower taxes. limited to mostly Etihad, singapore, delta and virgin. but can also be transferered to singapore at 1.35:1
Can also transfer direct to Singapore, Asia miles or NZ points, but some find them less usesful in aus, others more useful (this all depends on your needs and who you want to fly with)
Also with the sign on bonuses you will get more points with qantas as you are given 25k of qantas points vs 25k or ANZ points (which converts to less Virgin/SQ/whoever points)
Really depends what suits you and who you like to fly with.
Also Qantas is direct sweep, where ANZ you can choose when and where to transfer to at the time that suits. but you cant transfer qantas points, only direct sweep from the get go.