This poll won't get accurate results as far as the toughness or difficulty level as far as hunting deer or turkey, but more so their availability from one area to another.
If my area has more deer than turkey, I'd probably say that turkey are harder to hunt than deer, same as if I have tons of turkeys and few deer then I'd probably say that turkeys are easier to hunt.
With that said, turkeys have always been more of a challenge than deer for me. I've taken way more deer than turkey, but it's a totally different ballgame.
I can relax and just sit and watch deer feed around me without ever lifting my bow off the holder. But when turkeys get close.....I immediately go into stealth Predator mode. I'm wound as tight as a slinky ready to strike when I see my window of oppurtunity. Something about turkeys just triggers something in my brain and my predatory instincts take over.
I have hunted an entire season without turning loose an arrow on a deer, but watched many come within bow range.
On the other hand I have had a single encounter with turkeys and sent every arrow I had in my quiver their way......and left the woods empty handed.