I have been told (correct me if im wrong) ignoring aviaaiblity, the points required after conversion for the various programs is roughly the same, however it comes down to tax costs,
The points required for the various programs are not roughly the same. They can be on some routes and also when comparing on a limited number of programs, but in the main there area lot of differences and using the right program on the right route can save a lot of pointe, or $$, or both.
However one cannot get points, or at least useable quantities to all programs. Though having said that even for Australian residents like myself there are often marked differences.
Furthermore the differences vary dependant on the route.
One reason is that some FF program charge by regions. So if flying from the far edge of one region to the far edge of another there is good value. Also sometimes the regions are set from the airlines home-base and so this can provide some bargain routes.
However let me stress again that there is not the one rule of thumb. You have to look at where you want to fly and whether in Y, J or F. Y is normally not good if the FF program charges large fuel fines.
BURN
For example with Krisflyer and Qantas if you want to get to Europe while taxes and charges are similar, booking only the points are 161.5K vs 256K return and almost $1000.
QFF used to book on Cathay one way is 278K and $444.
So in this example KF is much cheaper on points. Cathay much cheaper on $$. Qantas metal probably the poorest value as if driven by points you would go KF and if by $$$ Cathay.
EARN
I'm my case I can earn at 2 to 3 Krisflyer Points per $ spent On Amex and under 1 on VISA/MC. Lets say I average 2.25.
Whereas with QFF the most I can get is 1.5.
So to get to Europe based on points earnt by spending my spend for KF is $72,000. For QFF it would be $171,000.
BUT one can also earn points from flying, hotels, groceries and the like and also credit card bonii. There tends to be a lot more deals that you can get to QFF than KF.
In my case I collect points in three main FF programs (at present this is Krisflyer, KF and Velocity. I still have some Enrich and I used to use BMI and Avios).
So I have various point stashes that I use and what I use depends on the route and cabin. Overall this allows me to outperform on both Earn and Burn as I take advantage of various Earn Promos as well as Burn Promos.
All of which means that the FF life is not a simple one, but by understanding the various opportunities you can really ramp up the value gained for your time and money.
AVAILABILITY
Most definitely DO NOT ignore availability. To do so on some popular routes may mean that you build up a points balance that is difficult to use. For the European example it is very difficult to fly on Qantas metal as they now have few routes and the ones they do you really need to have status to gain the seats. Krisflyer is reasonably easy to gain seats. With QFF booking on partners like Cathay is much easier.