I just learned about this this weekend from a major fabric company. The 68 is equal to what is sold at Walmarts, the 60 is the better one. If you feel the two side by side, you'll be able to feel the difference. Also, stretch it, even though it shouldn't stretch and a lot will stretch a little, some stretch. We learned about a very popular fabric company and one of the top selling fabrics, really stretches, which means it will not hold up as well. Notice, I'm not naming names as far as the fabric company or the fabric line. Take some quality fabric with you if you are getting it in person and compare. I'm very hesitant to buy online unless I know the company.
Craftsy does have a sale going on now, on patterns and fabric and when I signed in there was a code at the top that it was free shipping using that code. You can also use the code SPRINGDEALS and get a class for 20. Good luck on your fabric search. Just think about if you get it and it doesn't hold up, was the cost of the fabric really worth all of the hard work you put into it and now have it gone. Just saying.