First!
Advice to Yoshi players:
Learn the CG, this is what gives you an advantage of 6/4 Yoshi.
Link offstage is terrible; CG him off stage and even a well-spaced Nair can kill him. Spiking Link is effective but his recovery's so momentum driven that it's not always necessary. Link will throw projectiles/Zair etc to protect himself, I think your Nair eats our boomerang/arrows. Link can DI and momentum cancel to live forever- easily past 180%. Link can also 'whiplash' tether the stage if Yoshi Dtilts/Dsmashes him off. In other words, Link's recovery is terrible but he has a lot of tactics to help make up for it. Pressure Link offstage.
Link's good at punishing airdodges/spotdodges. Dair has strait 51 frames of mean attack, SpinAttacks punish airdodge>landings, Nair/Fair/Bair and projectiles work well too. But Link's air movement is c***: Use your excellent air movement to avoid these traps. Also our Uair beats anything Yoshi can do while directly above Link.
Link can deal with planking. He has 3 adjustable projectiles that work together. Link will find safe/mostly safe ground and spam Yoshi back on stage so don't plan on planking long.
Eggs>projectiles but Zair>eggs when spaced right. The spamming battle is heavily based on who has momentum. We're about even but in different ways, overall I'd say Link slightly wins.
Yoshi wins in close combat easily. Link has to play a difficult spacing game where we're just out of Yoshi's range. Again, yoshi's CG is really good for this MU. For Link being grabbed means being CGed offstage.
Yoshi's heavy but Link does have good KOing power if he lands the hit. Beware of Link's arrow lock (boomerang hits, followed by an arrow=forced stand up or free hit for Link), jab lock, footstool bomb>Dair, and chains like jab cancels, Zair>attack, bomb>attack.
Stages: Frigate is an easy win for yoshi. But it will probable be banned. Lylat/YI should favor Yoshi. Other stages are dependent on the players, Link and Yoshi both like the same stages. Even Brinstar. FD gives Link room to spam but at the risk of a long CG trip. Walk-off stages will help Yoshi's CG kill. As Link I'd CP Brinstar or PS1 but there really isn't a good legal CP vs Yoshi.
Be agressive, keep your momentum, hit/chain and run (or rather jump), go for CGs, DON'T RUN INTO LINK'S ATTACKS- we love spacing traps. That's my advice.
6/4 Yoshi.