ATAR wise, they scale the same anyway so look at other factors
e.g. which do you enjoy more / are better at? which has the better teachers? also look at the competition at school for each subject, go for the one with smarter peers for support
I'm doing Ext2 with worse marks than yours lol
From talking to my brother and his friends who did Ext 2, many people get awesome Ext2 marks but not necessarily high Adv / Ext 1 marks, and vice versa. It's weird, like Ext2 English is a totally different set of skills compared to Adv and Ext 1.