go for subjects you like above anything else.
the director of studies at my school showed me a little print out of the scalings of all the subjects, and if you get in the top percentiles of the majority of subjects they get scaled up.
personally, i really recommend physics. i know my class has heaps of fun, and the stuff is relatively interesting. haha no pun intended. but i know a few people who have just done ipt and they said its not relaly even like a proper subject. they didnt go to half the classes and still got high 90s.
i guess if you want easy, but boring, go ipt. if you want fun, but more challenging, go physics