The best way to get a handle on 'the exchange rate' is to look at what Week X in location Y at resort Z has as its stated "points required", look at the other system and see what it shows as "points required".
This could give you a general indication of "System 1 is generally 5 times the points of System 2"
Do please note, whatever you find on such research will not necessarily apply to every resort, every season, blah blah blah. The different points systems can change points required at any time for any reason.
You really must consider each system on its own merits.
Where do you want to go? Let's say Hawaii in January. Great, take a look at Hawaii in January to determine points required for System 1. Determine how much that amount of points would cost, both upfront cost and ongoing maintenance. Do the same with each system you are considering. That will give you a basic idea of what each system "costs".
**** BUT you must understand that each resort has a different, mmm, Desireability, so unless you settle on, say 5*, for each system, your results will not be that helpful (and even 5 star resorts vary - if you look at rental cost per night on a public site, that could shed some light on desirability). You could go the opposite spectrum: what's it take to get the lowest pointed HI resort in this system? Whatever, just do your best to compare apples to apples to get the most reliability.
Just do not expect points systems to be interchangeable. Like another poster alluded to, that's like expecting US dollars and Mexican pesos to be equivalent. ain't never gonna happen!!
Vicki Y.