CXB are the newer versions of the CXA. They put out more "light" more efficiently.
The trade off is they may cost a little more (but relatively insignificant) you'll also find CXA is lower supply. So just focus on the CXB.
The numbers - 3590, 3070, 2530 are the size of the cob from largest to smallest, highest to lower price and brightest etc.
Same goes for the Vero18 or 29's, they too have a V2 which is the newer cob. Vero are typically run at higher amps but lower forward voltage... Opposite for the CXB.. More efficient at lower amps but mor forward voltage.
To be honest the differences aren't all that much. Some will swear by veros some with Cree but we are talking about Chevy vs ford, both get you to where your going but in a slightly different ride.
Best idea is to just work out which you can get the cheapest they all go together the same way, operate the same way and all grow big fat green buds for smoking.
No choice is right on wrong, focus on what size... 3070 or Vero 29's or Vero18's and 2530's. Or go the big babies and get the 3590.
They all work