I'm light on for Premo Defenders, so I'd take others ahead of both Hurn & Sheppard... So I really don't know which way I'd go if I was choosing between just those two. Hurn has the proven history but he is 33yo in a couple of months and with a highly compressed schedule about to start... There's a chance Hurn may have a game off, like a lot of older players around the league. Also in a bit of a form slump.
Sheppard doesn't have the history behind him, but has been building these last 4 years and is in great form currently. He's younger so more likely to play every game in this compressed section of the season.
Sorry i'm not much help, lol