When equipment switch involves "swapping" items that have mana on them: If the switched gear item is "same" in both sets, the resulting mana remains "unchanged". But if they are a "different" then you loose the original items mana. i.e.you take off the old item (lose the mana) and put on the new item. I guess its fair, but should it only be the mana difference you lose, since technically you did not use your mana?. but that's a games decision.
When equipment switch involves "swapping" items that have mana on them: If the switched gear item is "same" in both sets, the resulting mana remains "unchanged". But if they are a "different" then you loose the original items mana. i.e.you take off the old item (lose the mana) and put on the new item. I guess its fair, but should it only be the mana difference you lose, since technically you did not use your mana?. but that's a games decision.
It isn't just mana. This happens with health and energy too. Its just the way the game is. This is why most players equip energy before they log off, do energy activities as the first activity when logging into the game, then switch to questing gear.
It is incredibly easy to get that lost mana and health back (wisps, mini-games, potion). Getting back lost energy from switching actually requires time or Crowns.
The real important issue here is the energy (as Oran stated). At the very least, what the game should do is give us a warning that energy will be lost (and how much).
KI looks at it as if we are removing an item so therefore we lose all it gives. Then we are equipping the new item. But what the game makers fail to realize is, we are wizards. Being a wizard means we could easily cast a spell to make sure our lives are not that much harder by a simple wardrobe change.
Either give us a spell we can cast to stop losing our precious utilities or give us fair warning before we do.