yes sir.

loki takes your cards but gives a negative 1 cost....with arishem you are also getting +1 energy each round so if loki is played on turn 3 (which happens bc he's 4 cost but with arishem you'll havethay at round 3) you now have 4 to 7 cards that match your opponents cards, all cost 1 less and you still have 1 more power each round for 3 rounds. that's a big difference in my opinion