It's time we had the chat Yea Forums. I love Castlevania games. CV4 and SOTN are two of my favorite videogames of all time,and I really enjoyed Bloodstained, but at the end of the day, BS is just a really great Castlevania game, whereas HollowKnight was an experience.
The things HollowKnight did better for me:
Better graphics and art style. Smooth 2d animations, and a rich, detailed, alien world, whereas BS is the standard medieval fantasy, in 2.5 which looks ugly sometimes.
Better performance. HK runs at 60fps on ps4 and never dropped in performance. Load times were also fast, and the game never once crashed. BS is locked at 30fps, has drops and slowdowns, and has crashed about 5 times on me.
Story. HK takes the win here by having a lore based story, similar to darksouls, where you learn about what you're doing and the world you're in by talking to NPCs and reading the tablets. The world is more interesting too because it's a post apocalyptic dead kingdom, not just another castle that looks like every other castle we've explored for the past 30 years with all the usual levels (clock towers, libraries, underground caverns, cathedrals, etc etc)
Game play doesn't have a lot of padding. A big chunk of the playtime in BS is grinding for mats and crafting. HK has very minimal grinding since you only need geo for buying stuff, and the map is big enough with enough to explore to actually spend most of your time actually playing the game, not grinding for shit.
HK takes the win for music as well. It's just more atmospheric and memorable. BS has some good tunes but I have a heard time remembering any of the songs, which is disappointing because I can remember almost every tune from SOTN.
HK WAAAY better boss fights. The boss fights in BS are just like fighting a regular enemy, but with a lot more hitpoints. The HK boss fights actually feel like events, and have awesome rhythms once you figure out the patterns, and are actually fun to fight.
overall, hk wins.