The numbers 50 and 220 are somewhat randomly chosen. There is no official scale or test. In theory, a std tire gets a wear rating of 100 and a wear rating of 200 would last twice as long. Nice theory, but with no standard, the manufacturers pretty much choose a number. Less than 100 generally means a competition tire, over a 100 means a road tire. However, a road tire with a rating of 140 may last longer and grip less than one with a rating of 240. Just the reality of it. The MX and the Falken Azenis are about the stickiest street tires currently produced. The Azenis do not come in a usable size for you, so if AX performance is all you care about, go with the MX.
That being said, the best to the worst street tire, may make 1 second difference at an AX, which is significant, but looking at the results, you can see driver makes 10+ seconds difference. The whole point of the SS classes is that pretty much any car in the class can win because none of the mods make that much difference.
Same theme, it is the driver, not the tires, springs etc. Many of the stock sub 150hp cars destroy the 300+ hp cars, because until two really experienced drivers are eeking out the last few tenths of a second, the mods or various tires are not going to matter and really just make excuses for why the driver lost.
To follow up on Curts post, I drove a stock n/a 944 for 5+ years before even trying race tires, sway bars or more than 147 hp (a little known secret is that Dan A. learned on a 944 as well, but don't tell anyone

). That teaches you to drive, 300 hp and race tires teach you how to go down a straight and spend money blaming the car..... so be careful, learn to drive, not blame the tires etc (except in jest or benchracing of course

)