CCM replica jerseys feel the most realistic. Nike made very good ones. I haven't bought a jersey for awhile, but like it was said, if this is for hockey practice, do not buy an authentic.
Honestly, there IS a difference, both in weight and how it feels. Also the authentic has the fight strap like someone said. Just buy a replica though, CCM makes good ones. What happens when you buy an authentic, and end up getting mustard or beer on it at a Rangers game? You're SOL. Ruined jersey. Better to ruin $75 than $300.