Mechanical heads aren't legal in my home state (Oregon), so the decision is already made for me at home, but I would not feel comfortable flinging one at an elk anyway. Fixed for me. I've hunted with Shuttle T's in the past, but currently have my arrows tipped with Alaska Bowhunting Supply's Samurai single bevel head, 125gr.
I use Magnus Buzzcuts exclusively for all my big game, from whitetail to elk thats the only head that will be on the end of my arrows. I took a whitetail doe last year at 72 yards with a magnus buzzcut, went through both shoulders and out the other side. Head was still in great shape, and if they bend/break whatever you can send them back and magnus will get you a new head or fix the head you sent in. Can't beat the warranty. Something about a big 2 blade sliding back when you draw just looks bad ass as well.
My broadhead of choice is the Fulton Precision - RAMCAT !!!! Fixed blade 1 3/8" cut. I have taken 2 P&Y Mule deer and a P&Y Speed Goat with them and nothing went more than 60 yards (GOAT).This year I am going to purchase a few packs of the ULMER EDGE and (CROSSING FINGERS) the Easton AC INJEXION 390 to play with.
Fixed here. Killed a big wild boar with a Rage a few years back. It worked, but after examining it after I retrieved the hog I swore I would never use another. I use a NAP Nitron. They have done me very well over the years. They're getting tougher to find! I'm hoping to let the air out of a big Az bull this year with one!