This week, after coming back from a two year break I was able to craft the weapon, neck, and a ring. The neck is powerful, but so is weapon Itemlevel at least historically.
I will only have one infusion to upgrade the pieces to 400+ this week. Which piece would you choose an why?
If you have access to high ilvl weapons outside of crafting upgrade the neck, if not upgrade the weapon.
Weapon damage will always be your highest DPS gain.
To answer your question, I think wep might be a bit more dps gain in your current situation.
Real answer: just get both. We’re only timegated on sparks, the rest is just grinding. Get to grinding some m+!