15's are a much stronger binding, but MUCH more hardcore.
I think you will find the PX15 starts at a DIN of 8, whereas the 140's would start at a DIN of 5..
Not sure how heavy you are, but for many people the px15 has a DIN which starts a bit high..
Agreed though, all things equal - for what you are doing the PX15's are probably better due to heel construction & wormscrew forward pressure.
Heavier, but overall much stronger binding.