Default [Q] Difference between SG3 Tab 10.1 Tablets?

Quick Question, I've researched SG3 Tab 10.1 and come up with 2 model #'s used interchangeably.. I don't know if its a matter of software, firmware etc. I've seen some similar threads but none that addressed specifically.. My question is:

What is difference between Samsung 10.1 in. Galaxy Tab 3, 16GB GT-P5210ZWSXAR and GT-P5210ZWYXAR