Typically the argument against HoB is that you can still easily pull off a clean combo full rage E into R in the knockup with Q->W->AA->Q->E->R
But the thing I like with Hail of Blades over Conqueror is the access to red tree, Zombie Wards are so good, Eyeball too, both of which near equally grants you the AD you miss out on from not taking Conqueror, Cheap Shot outdamages Coup de Grace, and Relentless Hunter is such a feel good rune.
The only thing I don't like is missing out on free boots + short cd smite/flash because I opt for Triump/Alacrity when running HoB.
Besides that, the argument saying you don't go HoB because you can still clean combo just breaks for me. I love the HoB rotation:
Q -> W -> AA -> Q -> Q -> Q -> E -> R, the damage is borderline retarded and it goes off so fast that you hardly have time to react and if you don't have a blink or hard CC you just die to it often.
At the end of the day it's probably a feel-thing, Conqueror might be more reliable over a large set of games seeing as it's like 80% picked or something, but all three of Conqueror, Hail of Blades and Electrocute are played by Rek'Sai mains in all elos so at the end of the day I think this is a playstyle / feel thing more than anything else.