Obviously I’d say go with your gut, because I trust you might know deep down who you value more, but just for extra measure:
I’m definitely saying Alberich.
I like him way more than MN solely for that mana gain and HOT. His revived come back in better health, get healed over time so they’re back in fighting shape after a few rounds, and also gain mana so they’re ready to fire their specials faster, that is, if they didn’t already get revived with full mana (because that’s always awesome too)
Zim’s cleanse is nice for the utility during raids, but Alberich does so much more than that. I mean, I like Zim and all, but Alby is on a whole nother level. He’s a life saver, literally.
Plus, increasing Alby’s life expectancy will have more of an impact on your overall play when compared to Zim. He’ll help your heroes survive longer, go off more frequently, and potentially revive them when they fall. Zim just wipes away the ailments, puts up a pretty minor attack buff, and hits everyone with the slightest scratch. Her fast mana makes her more playable, but honestly Alby is worth the wait.
Due to his slow mana, I think Alby would benefit more than Zim from emblem upgrades too. His biggest downfall is dying before he can go off, but emblemed up with a minion and stat boosts to protect him, he’ll be much more difficult to take down. Therefore, he’ll hopefully go off more frequently, or be even more of a nuisance to take down than he already is, (in some cases).
Alberich all the way