Guinevere --- Which troop is better?

I have a faced a number of guinevere tanks (over the now years) and have been using her as my tank for a while. I finally am about to level up a yellow mana troop to 23 (so 1 less tile for guin to change), should i switch out from a lvl 15 crit troop? I have noticed with that little extra def from a crit troop does a lot, especially with def emblems. is one tile worth 5% def addition? i realize the added healing helps too. and if i should switch after I hit 23 on my yellow troop, should i be working on a def troop to switch back, (I already have another lvl 11 mana) or keep going on the 23. thanks in advance.

A high leveled crit troop can help many tanks wich has their primary job as endure hits.
To me, Guinevere would benefit more from a crit troop.

Well personally I’m always attacking Guin with mono purple, and from my experience she’s kind of borderline where she needs a lot of emblems/troops to survive 3 tiles from mono. So I think getting her health/defense up to that point is going to have more value than increasing mana speed. If she gets killed from one tile match, mana isn’t going to do anything.