Messed around and got another Sigurd

Plus atk -hp is great. Keep that one unless you want a Sigurd that doubles. But I personally wouldn’t take the -def

My Sigurd is +SPD -DEF and I'd definitely recommend that one. Just a few more points put Sigurd in a different speed tier and do far more for him than a few points of DEF. I do run a high risk high reward build on mine but I've tried the standard with those IVs and it works well.

Keep the +atk one, +spd is nice but a def bane sucks for a tanky unit like him, plus you already built the atk boon one. Either merge or fodder for spd smoke.

I run a +ATK Sigurd as well, and he is an absolute beast. Keep that IV and either fodder or merge (Sigurd has some pretty good fodder)

Sigurd is an interesting character in that quite literally every IV (bar maybe -Atk in most cases) can work for him very well.

Whichever one you want to keep depends on what build you run most often. If you run a more standard set (Close Def, Crusaders, Bonfire, DD seal) I would stick with your +Atk/-HP Sigurd as the extra speed doesn't completely cover up all the lost bulk you get from -Def. If you run a more offensive build (Swift Sparrow/Fury, Horse emblem buffs with desperation etc) you'll find a lot more success with the +Spd/-Def Sigurd instead.

Personally, I would choose the +Atk/-HP as Sigurd's tanking and bruising capabilities far outclass his offensive capabilities (which every other Red horse arguably does better). The choice is still yours though.

Good luck!