Assuming you are earning at same rate for both QFF and Krisflyer, for Europe travel in business class, Krisflyer wins hand downs. On a limited number of flights/destinations you can get there and back for exactly half of what Qantas charge - with a stopover in one direction. However, for the same number of pts as QF charge there will be lots of availability (as you are on a higher award type) and more destinations, get the newer lie flat SQ product and can do stopovers in both directions. Or somewhere in the middle there are other carriers such as Thai..
For US, Qantas probably has better availability than UA or NZ (who you need to use Krisflyer miles on) but needs between 40-80% more points depending on where in US you are headed for.
My advice ... stick to Qantas (because the less people in Krisflyer the less people to compete with awards for
)
But seriously if you can get equal earn rates on a credit card that keeps the points in the credit card program, and allows you to decide from a number of options when you want to travel (including Krisflyer) that is probably the best option.