Which Owain is easier to save?

Well you could always run double Atk/Def bond since he wants to be next to allies anyways so that would easily cover a -Atk, and +Spd help's prevent doubles since he will be sitting at 40 Spd

So with double Atk/Def bond he will have 55atk, 40spd, 41def

My Owain is -spd+hp, glad I got him tho, from his introduction banner.
I think it would be easier to mitigate the attack, with the att/def bond seal and his base kit, a few points less in attack wont hurt as bad as lower spd.
His blue flame special allows him to hit hard, keep him next to his allies and he won’t really have attack issues.
Finally, to fix spd, you either need to have support or equip him with some skills.
Support isn’t always reliable, for skills, quick riposte and breakers will take up the spot for wrath, but can work.
I recommend going for the +spd Owain and using drive support for more spd and attack, and keep allies close in battle.
Btw, to fix my Owain’s spd, I gave him even spd wave from a spare Karla, love the character so much