Seeing as how Spawn is over 1,500x stronger than Link, all Link can do here is use hax and hope to dear God that he pulls something off.
Now, I'll admit. Considering Spawn is weak to holy weapons, and that Composite Link's Master Sword is holy thanks to the manga, Spawn could have a singular issue here. And considering Link can negate Spawn's regen, he can't get by that existence erasure anymore.
Also seeing as how both have precog and time stop, this could be a REALLY clutch match. However, I'd give it to Spawn.
Spawn's precog activates upon instinct, while Link's take place in his nightmares. He definitely isn't going to be sleeping in this fight, so Spawn has the edge of realizing Link's threatening qualities long before Link sees Spawn's. Seeing as how both are credited for their intellect on their profile, both would know what to do when the time arises. So it comes down to who would know when that time is first, and as I said, Spawn would definitely know first. Once he stops time, Spawn can destroy Link at his leisure. Mutilate him to death, tear him apart on a molecular level, and so on.
Finally, even if Link somehow found out first, he isn't even guaranteed to win. I see nothing on his profile nor the Triforce's profile that allows it to counteract something such as intangibility. Spawn could phase through him in the beginning and destroy his internal organs. And seeing as how his Hellfire Manipulation could just be generated to envelop Link and destroy him on a molecular level, I don't see Link getting by this.
If Link is somehow fortunate enough to find out Spawn's weaknesses before Spawn finds out his, successfully hurt Spawn once he stops time, all whilst avoiding anything Spawn throws at him and predicting all teleportation tactics and generated flames... in a time limit... then yeah, I'd give it to Link. Now, of course, this is actually pretty close considering that Link's hax allows him to get around Spawn's absurd power advantages... but Spawn's hax and power simply lets him stay in the game. I vote Spawn with mid-high difficulty.