Which game in your opinion was the better Metroidvania/Castletroid game? In my opinion it's Super Metroid. The atmosphere made me feel that I was really Samus, and I was obliterating Space Pirates. The fact that Samus was a girl helped. 

Castlevania.. the fact that Alucard is prettier than any girl helped.

Both are great games with excellent graphics, sound, play control, and game design. But I'd give the win to Super Metroid. Superior pacing, level design, and atmosphere give it an edge.

Gotta be Super Metroid. I think without that game Symphony of the Night probably wouldn't have existed as we know it. Both however are incredible games.

Sorry, I love Symphony of the night but Super Metroid FTW!

Is Symphony of the Night better than Castlevanias on DS? I'm thinking whether it's better to pick it up on Vita or just play the DS ones.

I'd argue that Symphony of the Night is better than all the "Metroidvania" games it inspired, with the exception of Aria of Sorrow. That being said, I highly recommend playing all the GBA and DS Castlevania games.

Both Super Metroid and Symphony of the Night are featured on my Top 50 list (#12 and #17 respectively) so while I do give the edge to Super Metroid, both are incredible achievements in gaming.

It's a tough choice which requires an explanation.

With the first castle on SotN and all of Super Metroid, you can only go through certain areas after acquiring certain abilities. Symphony of the Night's true ending unlocks the inverted castle though, and imo, the inverted castle is where Symphony of the Night falters. The inverted castle seems to be thought out if you think about it, but the way it plays feels like it was just tacked on. When exploring the inverted castle, it feels like you're just filling up the map and nothing more, unlike the regular castle and Super Metroid where you're actually making progress all the way to unlocking the inverted castle. The inverted castle includes unique items, new bosses, unique items, and a harder difficulty until you unlock one of the more op weapons like Crissaegrim, but it still feels like a tacked on experience compared to the rest of the game.

If you were to compare exploring the first castle on Symphony of the Night and ending the game without unlocking the inverted castle then overall the game is a much better experience in my opinion.

So my answer is mixed. Symphony of the Night is the better game, but in terms of overall experience and progression, I'd have to say Super Metroid though.

Symphony of the Night is, hands down, the best Castlevania game ever made.