I'm hit or miss with the human vocals - they're fine, I guess, but I definitely don't prefer any of to the VOCALOID version of any song. I'm a VOCALOID fan at the end of the day so in general there's only like, a few songs where I prefer human covers to the originals. Like for in-game songs, the Miku version of Usseewa is really bad, it came out 2 years after the original version w/ Ado so the song 1000% wasn't produced with syudou's super high-pitched tuning style in mind.
Whatever in-house tuning they're doing for the VOCALOIDs can be really awful though. I dunno.. It just kinda lacks any personality and sounds really flat a lot of the time. I think them sounding nasally is a voicebank thing though since Miku NT also sounds pretty nasally compared to her older voicebanks but I digress. I can't remember if it was true but I remember hearing a few years ago that they were using newer-than-v3/4 voicebanks for PJSK.
I wish they would either get the producers they're commissioning to do the SEKAI version tuning, outsource it to other people like they did with the SEKAI ver. of Help Me, ERINNNNNN! or just leave the original vocals when applicable like they did with Wah Wah World and Newly Edgy Idols. I'm sure part of that is just because Mitchie M did the vocals for those songs and he's like notoriously insanely talented with the program but still...
The Japanese rhythm game app Project Sekai ft. Hatsune Miku (Think it's called Hatsune Miku: Colorful Stage in english though)
It has a lot of entirely original characters (that aren't programs like Hatsune Miku) and subsequently a lot of covers of VOCALOID songs, both ones predating the game and songs made specifically for it.
It's hit or miss to me, some are really good but some are really bad. Sometimes a unit doesn't match with the song they're covering which is kind of unfortunate but I still think some can be great!
