Well, lets start at the beginning and figure out which colors you like to play, what kind of deck you like to play (combo, aggro, beatdown, etc.), and how you'll be playing (tournament or casual).
Basically means your win con is with general damage. Taken with that a lot of the Voltron decks tend to center around enchanting and equipping their generals to pump them up, ie Voltron style.
While not nearly as funny as all of the other posts here I actually thought it funny when I Rite'd my Knight of New Alara to make my Child of Alara a 36/36. I then swung with it for way over lethal.
Wish I had finest hour after that and been able to swing again because the Zur player wiped the board next turn.
Are we looking to be super competitive here? If so there are better cards. However, if you are playing EDH just for fun then by all means play it. A friend of mine plays it in his deck and it's hilarious when he drops it late game.
Vorosh just seems like he would be the best because of the color combination. Yes, Teneb does have a nice ability but it's not enough to make me want to give up blue for white.
Fun is subjective, that's up to you. As for which ones can win, all of them. It really depends on your meta and which other cards you put in the deck.
I know that's not the answer you wanted. However, if you want to go by by what's accepted here on the forums (For the most part) Captain Sisay would be the best bet for winning but also the most played out of those four.
Ayesha Tanaka - I've heard about some definite shenanigans with this general. It's also in good colors.
Jareth, Leonine Titan - Mono colored kind of brings him down a bit but opens himself up for serious board presence (White) and alpha strikes.
Reaper King - Opens up all colors. Has an obnoxious ability (This can be a pro or con depending on your playgroup). And can be fun to mess around with while playing freakin' scarecrows.
Edit - Though, those three usually are targets when they hit so take that as you will.
This....
Also, just be on the lookout for any things that don't target you and you'll be fine ( Withered Wretch, Nezumi Graverobber, Extirpate, etc.).
Wish I had finest hour after that and been able to swing again because the Zur player wiped the board next turn.
But hell, if you like the card just run with it. It's EDH.
Child of Alara - Wipe Recursion Beats
Nath of the Gilt-Leaf - Mass Discard and Disrupt
All very useful.
I would argue that GUB is actually a better color combination for the meta. Trade white for black. That's just me though.
And not really a bad choice among those depending on what you'd like to play.
Fun is subjective, that's up to you. As for which ones can win, all of them. It really depends on your meta and which other cards you put in the deck.
I know that's not the answer you wanted. However, if you want to go by by what's accepted here on the forums (For the most part) Captain Sisay would be the best bet for winning but also the most played out of those four.
Jareth, Leonine Titan - Mono colored kind of brings him down a bit but opens himself up for serious board presence (White) and alpha strikes.
Reaper King - Opens up all colors. Has an obnoxious ability (This can be a pro or con depending on your playgroup). And can be fun to mess around with while playing freakin' scarecrows.
Edit - Though, those three usually are targets when they hit so take that as you will.