“Perplexing”

“The knit fabric of this sweater is appealing, with great textural interest, a substantial heft, and deep, sumptuous color. But the sweater's fit is--well, bewildering. I'm a 12/14, so, following the recommendations of others, I purchased an XL (14–16) in the polo sweater by Blue Willi, and it fits fine. However, the same size (XL, 14–16) in this sweater has hugely deep, bulging armholes and a hemline that goes to the bottom of my bottom. Obviously it's too big. What's with Blue Willi and size variations? And if I exchange for a L (10–12) is it going to be too tight and clingy? *befuddled*”