But her aerials can cancel out boomerang....
Yeah, because getting a Samus in the air is a bad thing, especially when you've got a high priority up air. Samus is to floaty to do any good in the air. Note: you can't block the bomb with an aerial as the explosion hitbox is what matters, not the bomb. The boomerang is simply a buffer in between bombs.
Samus's recovery is way better than Link's, when you get low enough Link's projectile can be so much harder to hit with. Link fall much faster, and can only rely on his grapple and questionably good bomb jumps. Samus has bombs, Smash missiles, homing missiles, and a dair to edgeguard with.
Samus' isn't recovering against Link, she's dying off of the top, from which there is no recovery. Samus' recovery can be extremely predictable due to the slow nature of it. If you try and sweet spot beam, Link just falls off of the ledge under the beam, jumps, and bairs, forcing you to use your up b. The same could be said for link, except Link is much quicker in the air then Samus, and falls faster, making him less predictable. Plus his hook shot is faster to reach the edge, and he can "bounce" over the Samus from far away, or fall below the edge for a sweet spot.
Samus bombs aren't that good for much of anything, sans shield pressuring and recovery. The dair is a meteor smash, and is therefore cancelable, not to mention relatively tricky to pull off. Homing missiles would only be a problem when recovering, and even then you just up b into them AND THEN hookshot, instead of attempting a hookshot and getting missiled in the face.
Yes, Link's arrows can block projectile, but then what? Unless you feel like firing another arrow, Samus can outprioritize any projectiles with he awesome ftilt.
Samus' missiles are extremely predictable, wherein Link has multiple options for his boomerang, his bombs following an arc pattern, and his arrows completely shutting down Samus' charge shot and missiles. Also, Link can throw his boomerang faster than Samus can shoot missiles if he is close enough and he catches the boomerang on the ricochet. This is heavily reliant on the distance between him and Samus, and even at farther distance when this doesn't work, it just makes missiles easier to dodge.
You can't out prioitize the bombs, because they explode, creating a knew hitbox. By simply f tilting the projectiles, you are putting yourself on the defensive. If the Link just keeps it up, he'll find a hole and punish it.
Good luck with that.
It is true that Samus is not quite as good at close range, but she still isn't a 7-3 match. Her nair > all, she can CC dsmash, ftilt is fast, can be angles for shield stabbing, and good priority. A grab to dthrow goes into almost any attack at most percents. Her bombs can be used for more than recovery -- SWD'ing, or pressuring your opponent. Her dash attack has great priority, is fast, and has good range.
I would agree that 7-3 is a little extreme.
Her nair is good, but it is also dampered by her high short hop and slow fall speed, problems which Link does not have.
Link is also a proficient CC'er.
F tilt is laggy enough to be punished if shielded (up b out of shield or shield grab down throw up air).
Samus will rarely get grabs, and even then her down throw can be easily DI'd away from and then teched.
SWD isn't a key technique to being good with Samus, and even then, you aren;t using the bombs for anything anyways. I already said bombs are good for "pressuring", but only if they shield (i.e. run at them and triple bomb their shield followed by a dair).. If you just keep bombing, the Link will just smack you with projectiles.
Her dash attack can be shielded and punished easily. Link's projectiles and shffl are harder to due l-canceling. Samus can't shffl effectively due to slow fall speed and high short hop.
Now is the time you pull out the "Samus's grab sucks" card, right? Right. Yes, it does suck, but it 1) can be lengthened and 2) isn't used so often anyway. Her upB out of shield beats almost anything, and can be done out of shield.
Link's grab also sucks, but works more so against Samus then vice versa to the sheer amount of ground moves Samus do due to non-existant shffling.
The extendor isn't a key move in Samus' arsenal, and I find using wouldn't break the match.
Up b out of shield is easily punished if you see a pattern in the Samus' defensive game. If the Samus is consistently Screw Attacking out of shield, sffl an aerial and then shield, followed by up air or dair. If the Samus catches on, and doesn't spam it, her only real options are to WD out of shield and tilt, in which case you shield the tilt and retreat for another projectile war, which the Link should win anyways.
In this situation, the Samus can try and mindgame a grab, but is easily punished with a dair if missed.
There's also the issue of stages. Samus likes big stages, with or without platforms. Platforms help with platform missile canceling. Bigger stages highlight her recovery skills. Now how many stages fall into these categories? Nearly all random stages. She can counter pick Dreamland (which is random). Samus can DI anything (almost) you throw at her and still live. Huge ceilings help with her floatiness..
Platforms also help Link avoid missiles and help with his projectile game, considering his boomerang can be thrown downward and upward, and his bomb follow an arc.
Pokemon Stadium's ceiling is the second lowest of the neutrals (following YS), and almost all of the transformations help Link control the area with projectiles (fvck rock).
Battlefield is my favorite neutral with Link, due to the platforms and the bottom center which can be grappled as a mindgame and to help recover in a tight spot. The same can be said for Samus, but her up lacks some of the vertical and horizontal recovery that Link's has, making this more risky for her to perform. This stages ceiling isn't high enough to pose a problem.
YS and FoD are both bad stages for Link do to the lack of projectile spam capabilities, and also because FoD has a deceptively high ceiling.
Dreamland poses a threat due to the aforementioned reasons, but is still winnable with Link.
Samus is best played as a defensive character, just like Link, except Link is better at playing defensively against a Samus due to the best defense is a good offense mantra, being that of the projectile spam.
Zelda is a bad character, but is still a soft counter to Jigglypuff.
Edit: it should be known that I am currently bored at work, hence the wall of text.