While great to have, the differences at ledge and ability to stock trade aren't enough to make Chrom better IMO.Fine, I'll actually talk about the character I wildly defended for half of v4.
Chrom has more advantages over Roy than just a consistent sword. His ledge pressure is better, thanks to having different animations on his ftilt and jab that cause them to hit below the ledge. Then there's the fact that he can convert basically any low % hit into a stock trade, which people have been figuring out ways around, but is still an immensely powerful option.
Even with those, there are still people who think Chrom is worse, and that people aren't exploiting his flaws enough (which they definitely aren't, whether or not he's better than Roy).
As far as Roy's kill power goes, he basically needed a read to kill. He had kill setups, but none were really reliable, and the few confirms he had were hard to, well, confirm. Side-B, which would've been a great kill move, didn't ****ing work, and Bair had terrible hitbox placements that made sweetspotting it prohibitively difficult. Fair didn't kill until like 150 if you were even slightly off of the ledge, and Dash Attack was way too linear to reliably catch people.
No, that proves nothing. The idea that Roy's design is fundamentally flawed existed long before Chrom did, and very much has and will carry over into perceptions of who the better character of the two is. If Chrom continues to be considered better than Roy, that just means that most people think Roy's design is fundamentally flawed, regardless of whether or not it actually is. In other words, it means nothing has changed.
Chrom has the speed of a character that needs to get in, and the sword of a character that doesn't have to. This makes him vastly safer than Roy in pretty much any neutral interaction.
If you stay around Roy's tipper range, you can generally poke or keep him off of you. Chrom is going to be a threat, period.
When we had the Lucina/Marth debate in S4, despite (funny enough) Lucina also being able to hit lower and more consistently, it came down to tippers. In the end of S4, you could hardly compete without some sort of character-defining X-factor.
Marth's tippers - and the fact that he had ways to confirm into them - ended up tipping the balance for most people, though the characters ended up closer and closer together.
Here, we have less need (so far) for an X-Factor - just some way to close a stock in general. Chrom is going to win neutral more often than Roy, and can play at more ranges.
...
All that said, depending on how the meta goes for brawlers/grapplers, I can see Roy improving. In this meta, though, I don't think he's particularly great. A brawler with the frame data of a sword character is rarely an amazing combination.
But I could be wrong.