D&D 5E A rare multiclassing opportunity

Hi, I play a level 13 Totem barbarian in a game where I can switch up and change my totem choices over a long rest. Recently, I got lucky and found a headband that makes my wisdom score 18. Whilst 14th level totem abilities look cool, so does dipping into War Cleric for bonus action attacks and then +10 ON TOP of Great Weapons master as well. Our campaign is ending soon, probably 16th level at most.

Should I stick with Totem Barbarian or go with War Cleric?
(Both make equal sense from an rp standpoint)

Thank you

The level 14 totem barbarian abilities are good and can be used all day long. I would lean toward taking them first especially as you can change them out at the start of the day. Warcleric has a good case at level 15 or 16 though.

As a quick point of order - you need to have a 13 WIS to multiclass, and many DMs require that from your natural scores. Do you either already ahve the 13, or is your DM okay letting you multiclass with the item?