Maybe it comes down to which type of game you like more, so I don't think you can say one is better than the other.
SotN introduced an entirely new genre of Castlevania games. This and the music and art is above any of the other CV's (aside from Lords of Shadow actually). For this reason, I would say it is better because it influenced more games. Plus, the inverted castle was pure genious. However, it isn't the most polished of the 'Metrovania' form. I don't think any of the successive CV's in this style has really topped what they started in SotN, though I think AoS would have come close had the technology allowed it (that, and a larger second castle).
I've got the Saturn version of SotN as well and agree with what everyone says - the things they added are outweighed by the things they changed. It's not worth tracking down the original unless you're really hardcore, and even then I don't think it's worth $70. And if you want to play the Saturn version, use an emulator (there's a LOT of slowdown on the actual hardware!). In many regards, the PSP version is definitive because it took some of the things from the Saturn that were done well and added them. Unfortunately, Alucard's new voice acting is sub-par, so I prefer his PS1 sfx - and I really wish they'd found a way to integrate Chaccone c. mol. *sigh*
Dracula X was in many ways a polishing of the level-based Castlevania. Difficulty is very well-balanced and the item crashes and alternate exits added new things and brought in the best from Castlevania 3. I've got a few gripes about it though, but they're really quite minor. For one, I wish they'd just written 3-minute long songs instead of 1.5-minute songs and looping them. Second...no whip flick! I still think Simon from CV4 is the best

(that, and he could crouch-walk

)
Anyway, I'll go with Dracula X Chronicles, which has all three versions for under $20. You can also use a video cable to plug it into your TV or take two of the best CV's ever made on the go
