OK, So I'm having a little problem with a speed tune i'm currently working on. Well, it's more of a single champion issue that is going to be a part of my speed team that im having difficulties with. Basically, I have two level 50 S tier Decrease DEF champs and I can't decide which one to rank up to 6 star. The 2 champs in question are:

Drum roll please...................................................................................

Stag knight

Warmaiden

Now I know Stag knight is probably the better choice being basically a legendary having DEF AND ATK Down in his A2 for 2 turns on a 4 turn cooldown. But...... i'm really doing this speed tune for the arena so I can make it to Gold I (Hopefully) and while the extra Decrease ATK is nice, Warmaiden offers the same DEF down in an AOE that has better DMG multipliers. And being a rare she will be much easier to book ( currently have 5 books on WM, and have used 3 on stag knight) Yes, I did pull them weeks apart from eachother. S.K. I actually got from one of my first ancient shards! (before I even knew how strong he was)

So you can see my dillemma in that I intend for either of these champs to go second after my speed/turn meter booster, yet I know warmaiden will hit harder and I should be able to max her very soon whereas Stag knight I wont be able to book completely probably for weeks or even a cpl months because I don't spend money on books. So This will limit me on my cooldown reductions and DMG increases and Buff/Debuff chance Percentages that I could have gotten easier on warmaiden. Her kit is all around better for Attack also, and really having 3 nukers on my speed team rather than 2 sounds better. I am weighing in my head how beneficial the extra Decrease ATK would be in arena battles with Stag Knight, if I find myself in more fights that last longer than 2 cycles. Yet, I can't help but think that more than half of my arena battles last not longer than 2 or 3 cycles at most. So this is where I could possibly benefit from Warmaiden having that extra ATK power. Also, I know you can make Stag Knight's Attacks decently strong also, but Ive already got both of them pretty much built how I want them with Warmaiden putting out far more power than stag knight and S.K. having more ACC, Survivability, HP, Etc. 

 If you guys could give me some feedback, and let me know what you would do I would appreciate it and hopefully it will help me make a decision as I'm close to being done farming for 5 star food ( 4 down, 1 to go ) Thanks!

BTW - If it helps I can take a screenshot of my gear, ETC. just let me know. The team I intend to use for this build will be; 

                -   Starter - High Khatun 

                 -   2nd - Stag Knight/Warmaiden (Defense DOWN AOE Attack)

                  -   3rd Nuker - Kael 

                    -  4th nuker - I have Ninja at rank 6, and Chonoru at rank 6. She is strictly attack and admittedly somewhat fragile having geared her for all out attack, but she has the highest attack rate out of all my champs! 

*I think if I go with Stag Knight, for that extra Decrease ATK, Ill use Chonoru with him. They will pair well after my first turn, her A3 is an AOE that removes all Increase DEF from enemies, then attacks all enemies. That, coupled with Helmsmasher mastery I have on her make for a SOLID hit completely ignoring all enemy DEF with Stag Knight, and the extra ATK down debuff will help ensure she stays alive for my second cycle to use this incase the enemy Buffs DEF After I start.