Which, of course, is nothing more than your personal opinion, as you can't speak for people who legitimatelly like SCIV's OST better than SotN. It's not always about sound quality, son. Composition, harmony and melody play a huge role too, and SCIV pulls it off with flying colors.
I just don't see how anyone who is neutral about castlevania like me can prefer SC4's soundtrack over SOTN,it has some of the most boring,drab soundtracks in all of Castlevania.
Castlevania music generally is rock/synth and something that is just exhilarating and energetic not this boring moody 16 bit organ composition of SC4,in fact its like an oddball in the entire series.
SOTN stays true to the originals in terms of the soundtrack and contrary to your opinion the sound quality makes it excellent.
Just for comparison's sake just compare Bloody tears from SOTN to SC4 :-
SC4=
https://www.youtube.com/watch?v=QOWUSsFar-sSOTN=
https://www.youtube.com/watch?v=tgkxSkF7QOUROB=
https://www.youtube.com/watch?v=WqWW0PTkjR8SC4's blood tears sounds like its muffled or something its not even better than the ROB red book version SOTN's bloody tears sounds excellent.
ROB's Vampire killer puts SC4's vampire killer to shame.
ROB=
https://www.youtube.com/watch?v=vlayiIBH75oSC4=
https://www.youtube.com/watch?v=D5mMEyMoXB0Seriously objectively speaking SC4 has some of the least impressive soundtracks in the entire series.