In the past year alone Santos fell as much as 70% whereas WPL...

In the past year alone Santos fell as much as 70% whereas WPL only fell about 35%.

If oil were to fall to $10-$20 then Santos' debt would become junk or worthless. Conversely and as markets have become optimistic with oil rising to $50+, that debt becomes priceless and therefore STO has risen more than WPL, even on days where it may not have made sense.

Still if things turn south again, which they will because US production and inventory levels have been hardly dented, STO presents greater risk than WPL. You can go for the easier gains but you might go broke doing it.