I like three broadheads

zwickey 2 blade eskimo
magnus I 2 blade
simmons land shark

which one is going to be the easiest to sharpen, and which one will hold an edge best

I'd have to say that the Simmons will hold it's edge best, butis the hardest to sharpen (without the wheely thing) The Zwickey & Magnus are around a 50/50 split on ease of sharpening.

You generally find, with all blades, not just broadheads, that the easier they are to sharpen, the quicker they'll lose their edge. Simply because soft steel takes an egde quicker, hard steel keeps it longer.

If it was a choice between the 3, I'd personally go with the Zwickey, simply for ease of sharpening. Don't forget, you don't need good edge retention on a broadhead. It's not like you're gonna be making repeated cuts with it! Just the one & then either retouch or write it off as lost  :D