The 1st printing and revised 2nd printing of the Hedge Knight trade paperback came out first from the comics' original publisher; the 2nd printing contained, additional new material and is generally a bit more collectible--it also has a different, variant front cover, too. (I have both, along with the orignal comic issues and their variant covers.) Be aware which issue you're looking at.
Marvel's later-produced hardcover, while quite nice, is newer. I suspect it had a larger print-run, too, which may account for it being currently priced lower; not having looked through a copy I don't know if it had mutiple printings, which would be a factor in its the collectible price. I've considered buying the hardcover but so far haven't; I should probably do so before prices begin to escalate out-of-site.
If I was going to buy just one of these, though, it'd be the revised 2nd printing of the first trade paperback. But I'd check the most recent Overstreet Price Guide for some guidance on current prices = collectability.
Edited by Ser Kennos of Kayce, 24 November 2012 - 02:12 AM.