I would think that Relentless Edge would win out by comparison. However some circumstances could weight that another direction.
Are you making full use of the expertise on Inevitable defeat? If you would drop below the exp cap without it I would say stick with the mace till you can adjust else ware on your gear or spec.
Keep in mind that the haste rating on the polearm is not a very valuable stat for an Arms warrior. (Lowest SEP value DPS stat.) However the higher base DPS, the higher crit and no loss to AP make it a superior weapon winning out over the faster swing time and as long as you didn't loose your exp dodge cap by switching.
Another issue is if you've already gemmed for ArP mace spec may be more beneficial for you.
Just looking at the stats on the two relentless edge is a marginal upgrade if you're making full use of the stats on both weapons. But with 78 expertise on the the mace, that seems unlikely to me. You're either well over soft cap with the mace or well under with the axe. Tricky situation.