as it stands, on paper arms is always going to beat fury over medium-long duration fights. if you aren't mastery boosting a death wish pre pull, then you are making fury fall even further behind. that said, fury is still viable on pretty much every fight for progression (except H-yorsahj).
also, using two like ilevel gurths is a bad idea. I talked about this in a different thread but I'll summarize it in a single post:
-Certain attacks can proc gurth regardless of what hand it's in (the most notable being BT).
-if you use two of the same ilevel gurths, the spell id's of the proc is obviously the same for both weapons.
-When you use an attack that can proc off a gurth in either hand, it will not proc the same spell id twice
-different ilevel gurths proc different tentacles (read: different spell id's).
-using 2 gurths of different ilevel allows the attacks that can proc from a gurth in either hand, to be capable of procing both at the same time (this has been confirmed).
TL;DR: if you're going to use two gurthilaks, make sure they are different ilevels, otherwise you are losing a lot of stats for a minuscule increase in tentacle procs.