Which Brave Ike? +atk-def or +res-spd

Unless I luckily pull more copies with my nearly-zero orbs, one of these two will be used to inherit Steady Breath to my +def Nowi.

+atk is great, but -def is not. I know it's somewhat made up for with 4 def from Steady Breath but I'd rather not lose any def at all. This is the first one I pulled on his original banner and I already inherited QR 2. I haven't been lucky enough to get much QR fodder, so I'd hate to waste it. My Nowi already has QR too.

+res helps with magic a little (23 is still pretty low), and -spd helps charge special with Steady Breath. Does -spd help more than it hurts? Is it worth wasting a precious QR inherit to start using this as my main Brave Ike?

BTW, I almost exclusively use him on my Aether / Tempest Trials team. Thanks in advance for the input.