im not sure when MagnumXL's first hit the market but when they came out i tried them and found them a little loose and my well fitting regular magnum, but this year (i am 22) i tried them again and found that they fit great, so i guess i have gotten a little thicker, wich is suprising because nothing besides my waist has really grown in the last 2 years.
now i love the XL's and wont use anything else, magnums are a little snug on me, and if i use a cock ring i strain even the XL's!

anyway both the magnums and the XLs are about the same length and the XLs are just a bit bigger around, I'm thankfull that i can get something that fits me well off the shelf at walmart. and my wife is thankfull that um .. well lets just say she's happy :P