Brave Ike IV's ?

That's a surprisingly hard question. It depends on what you want to do. In my opinion you have the choice between a tank (+Def) or an offensive baiter(+Atk).

With a Def boon, you're basically impervious to melee blues, arguably even melee greens. And the -Atk isn't "so bad" since your damage will come from Aether + Threaten Def. Just use the base kit + Quick Riposte + Close Def seal if you have it.

With the + Atk you can run a more offensive set, with Bonfire / Draconic Aura since it will proc right after you've been attacked. You can also run the Aether set as well, you just have to be more careful since 24 Spd is extremely slow (also a superbane).

I personally use my Bike as a melee tank, so as crazy as it sounds I would take the +Def -Atk one. It just depends on what you need him for.
Either way, he's an amazing unit.

Like Artorias says, it's actually a hard question. Well, would not be for me really since I see him as Steady Breath fodder in almost every case and with those IVs would not hesitate.

Spd is a superbane though so that's something to consider and that Def boon with SB really allows him to tank physical threats.

Wow people are not liking -Spd Bike apparently.

Coming from someone who has a +Atk -Spd +8 Bike he's really good. Urvan wants you to get doubled and -Spd helps with that.

Overall imo. +Atk -Spd/+Def -Spd is the best for unmerged and +Spd -Res is the best for +10.