Alright I'm going to explain why WWL is most likely to win. First of all the most likely showdown that happen is one between him and TPL (let's face it most of the other Links are pushovers compared to those two).
WWL has the Parry which serves as an instantaneous Helm Splitter and Back Slice which can be used to quickly counter many attacks. TPL also has the BS and HS but he can't do either of them instantaneously and definately can't use them to efficiently counter WWL. Point WWL.
Then the Hurricane Spin. WWL has this and can easily use it to cause massive amounts of damage to TPL and veery quickly. And if used strategically he won't become dizzy (like running into walls while TPL is sttunned). Point WWL.
TPL has the Mortal Draw which is dangerous but don't forget WWL's Mirror Shield. It can easily block it without much (or any) damage to WWL. Plus if he dodges it then that leaves TPL wide open. Point WWL.
TPL has the Great Spin which can be countered easily with the Parry. Point WWL.
Most of the projectile weapons of both Links would be useless against each other but WWL's Ice Arrows even if shielded against would freeze TPL allowing him to whack him with his hammer. TPL's mace is often considered a great advantage but really is quite the opposite. While it's extremely powerful it isn't very accurate (in fact it's very easy to dodge) and while TPL pulls t back that gives WWL a window of opportunity to attack. Two points to WWL.
Now to their achievements...
TPL actually killed Ganondorf while he had the ToP which is an amazing feat. However TPL would've been screwed several times if he hadn't been helped. Yeah that's right TPL had backup when he fought Ganondorf. And alot of it. 2 people, a horse, and 4 holy spirits. WWL however had only 1 kid his own age and a dusty old spirit king. Hardly any help at all. Then there's the fact that TPL's battle with Ganondorf was long and drawn out while WWL's battle was reletively quick. Heck WWL even defeated Ganondorf before he could go Ganon on him and Zelda unlike TPL who had to go through a fight with Zelda as a puppet, a fight with Ganon the beast, a horseback battle with Ganondorf and his spirit minions, and finally a classic sword duel. Chalk up yet another point for WWL.
Now for their experiences prior to their respective adventures...
WWL had been a simple sea boy on a quiet, idyllic island and had virtually no sword training prior to his adventure and yet did surprisingly well. TPL on the other hand was a farm hand on a farm in a peaceful forest and he had years of experience with swords prior to his adventure and also did very well. TPL gets his first point.
Now for miscellanious factoids...
WWL is a very quick learner (this is illustrated by the fact that he quickly learns to play the WW, sail, and fight) while it seems TPL tends to take his time more in learning translating to a slower learning rate. Yet another point for WWL.
I could go on and on about all this but then my post would get too long and we don't want that. As you can see it looks very grim for TPL in the face of WWL. A classic matchup of youth vs. experience and youth kicks a**.