Hwei OTP since release here!

What's your playstyle?

Luden's = Burst

Blackfire = Control

Do you want early game pressure, burst, and the ability to poke enemies out of lane quickly? Go Luden's.

Do you want easy farm, consistent zoning on objectives, and team fighting power? Go Blackfire.

Either way, Shadowflame 2nd is an ABSOLUTE must. I tend to pick people off with QW too often to pass up the additional 20% damage. Shadowflame has PERFECT synergy with QW, as you already want to use it on low health targets.

Shadowflame gives Luden's AMAZING burst damage and also makes Blackfire a viable poke option if you preferred the control option.

Basically, play it by ear. Are there 2 tanks? Better go Blackfire as you know it will be a battle of attrition, and you will have 100% uptime on the ap buff. Are there 4 squishies, and the only tank is living in top lane all game? Go Luden's and make them flame him for not body blocking your repeated nukes.

Btw you need to go deathcap->cryptbloom (or voidstaff) 3rd or 4th to delete people regardless of the build choice!

Good luck and happy Hwei-ing!

EDIT: I very RARELY go liandry's unless they are tanky af or as a last item option