Warren, that is not a penalty clause, it is the calculation of the overtime rate. You are correct with regard to the various differences in the rates for overtime calculations.
By penalty clause I mean that additional hours are paid above the work done, ie in the J* contract, section 25.5.4 working on a day off attracts a "days pay" plus an additional "days pay" - effectively 8 hours pay (subject to annual hours flown), regardless of hours flown in that duty. J* have more days off in which to attract the payment per roster.
J* also have an additional 2.5 days off per roster period (28 days QF, calander J*). At about ~850 hours per year this equates to double time. Virgin get min 5 hours on a day off (also ~11.5 days off per 28 day period). QF do not get any of these. At best, they may get an "bonus hour" for being called off reserve (min 4 hours pay) to do say MEL-SYD-MEL. But say a MEL-SYD-BNE-MEL off reserve is flight pay only. My info is that for QF, 95% of hours paid is hours actually flown.
J* also have a retention payment in addition to a profit share scheme (QF have profit share only)
I was very clear when I said "basket of hours". At first blush, the QF contract appears to be substantially better on the headline rate. As usual, the devil is in the detail and one needs examine closely all three contracts in their entirety and imagine the real world of 12 months flying with the usual roster disruptions and number off available to be called on, and the various penalties that apply. I think if you sat down with a spreadsheet and played around with some numbers that all three contract will very close in earning potential for a given basket of hours in the real world.