This is my current team:
Surprisingly this has been holding me in Diamond. I am about to have Mitsuko ready at 3-70 as well. My next decision is who to ascend to max, Santa or Mitsuko? I am interested in who will help me out mostly overall, and get more use:
Who is worthy of my first 5* red getting rings?
I think Santa is a better tank—indeed, a very good tank. Slow, but he has the heft to survive it. I really like Mitsuko’s design, but I’m not yet convinced of her on defense.
I really like Santa over Mitsuko as well. He’s also very fun to play with on offense.
Another vote for Santa over Mits
Is “neither” an option?
Sure, but why? I think these are two very solid heroes. GM is clearly better, but I’m not certain that there are other reds that are clearly head-and-shoulders above Santa and Mitsuko.
Santa.
Mitsuko is a solid hero, but her biggest asset—the ice reflect—can be bypassed by a foe simply not casting ice specials for the duration, or just bringing a stack against the flank (e.g. red or purple or yellow).
Then there’s people like me that have GM and Santa and are contemplating best way of using together. 
I answered assuming the “two” were Santa and Mitsuko. If GM is an option, life becomes more complicated. Santa is a “old school” tank, with huge survivability and a “oh 
” special, while GM is the “new school” “I will kill you all now” tank. Probably need to put Santa tank and GM flank.
Really? Two of same color next to each other?
I was thinking Santa tank and GM wing. Especially for wars as GM will also benefit from the field booster.
Haven’t tried this. Still low on rings so focusing on other heroes - just got Wilbur so he’s number 1. Santa will be coming up soon.
I normally avoid adjacencies, but there are no blue heroes with a hit-3 attack pattern. Athena is the worst, with red-strong splash. GM wing would work fine, too. Depends on what else you’re running.
I have Santa and 2 Mitsukos, with enough mats to level 2 of them. We’re using red tanks most of the time for war so I guess I’ll go Santa with MN and Drake/Inari flanks, Misandra and Sartana wings until I get Kage and Victor levelled.
Wish Santa wasn’t slow mana… Have come across a couple in raids, but not enough to judge his strength. Each time I get really good boards so Misandra + 2 Tritons make short work of the opposition.
Was thinking of playing Mitsuko tank, flanked by MN and Inari…
In wars if your whole alliance is using red tanks, a Mitsuko tank is an invitation to omit blues (saving them to destroy one of your allies) and stack something else against you. Santa forces your foes to bring out their best blues against you, leaving them short on their other attacks.
Cheers for the assist! That definitely helps with the decision making. Santa it is first, then Mits 
I agree with you fully that Santa is the better of the two. Mitsuko is slightly better for offense, but significantly worse for defense. The problem is that Santa gets completely countered by a Kiril, who ends up being an auto add to any raid team against a Santa tank. There are two TC20 available red 5* (Marj without question, and I firmly believe Azlar to be better for defense than Santa and Mitsuko as well as better than Mitsuko for titans) that could get mats before either of these so it may be worth discussing holding back and running 4 tc20 (would average roughly 1 basic 5* every 10 days) for a while, hence the “neither” suggestion.
Unfortunately my 5* reds are lacking. So no other options.
