If i wanted to go through entire series, should i play Rondo of Blood or Dracula X?

I've never seen anyone say they enjoyed Dracula X over Rondo of Blood. Admittedly, I have not played Dracula X on SNES, but I can say from personal experience that Rondo of Blood is awesome. Also, Rondo has a stellar CD quality soundtrack.

Rondo Rondo Rondo. Get it on Wii Virtual Console (can be played on Wii U via Wii Mode).

I would say if you really want to play through the entire series play both.  They are very different games.  Dracula X is like if you played Rondo of Blood and then were tasked with creating a port from your memory.  The overall concept is similar but the level designs are different.  After playing both I am glad I did.  It's one of those crazy video game legacies that I find to be fascinating.

Rondo of blood is available on Wii VC as well as the PSP as Dracula X Chronicles which includes a remake of Rondo of blood as well as the original and Symphony of the Night as unlockables.

Rondo is a far, far better game than Dracula X. I can't recommend the latter unless you're some kind of series completionist.

Having now played Dracula X for the site's review, I can attest to its horribleness. It's Rondo without any of the things that make Rondo good, and also without the gameplay improvements that made Super Castlevania IV so enjoyable. It is also brutally, unforgivably difficult--especially if you're trying to save both women.