Recommended Weapon refine for S!Alfonse

I pulled a +Res -Atk Alfonse on this banner, its probably his worst IV spread but I'm ftp so I'll have to deal with it. Due to his loss of attack I'm wondering if I should refine to +atk or +spd on his weapon. He's on my cavalry team so he reaches 39 spd with hone cavalry right now.