Authentic jerseys are more expensive, and to me, less practical. Why would you pay extra for them?
The Jerseys are Better Quality
The Stripes Decals are Stitched on
I think ALL of them come in GIANT sizes. Personally... I'd love an authentic one, scaled down - little - so I could dream of being tough. Dream as I might wearing my authentic autographed jersey, I don't look tough at all in it when it's longer than every dress I own. It is very well made though, stitched decals, just as Onknight said.