Little things.
B/C could be merged honestly. There's nothing that any of those characters do that put them clearly above anyone in the tier below them, while C tier has a few characters who could make the claim of being in the space above them. Krrrrby for example has solid offstage and good onstage kill power but it held back in terms of sniping by his poor drift and lacks any truly decisive neutral tools on-stage. His greatest blessing there are Dash Attack, MK Dthrow and horizontal Side-B but that just translates to better punish than neutral. Solidly mid, when you add it all up.
Snake's most prominent representatives are one S-Tier player and one A/A- Tier player. His punish and survivability are OUT OF THIS WORLD but they kind of have to be because the man takes a real beating. Worst aerial mobility in the game and his only off-stage mix-up being *blowing himself up* are no joke. Prolex make it look good but it takes a very specific sort of player to make Snake work, and Snake almost always has to put in more work than the other guy just live long enough to blow up that C4. I could see it coming close but Snake has huge weights on either side of the scale. Very balanced.
I will give you Marth. (Sorry, @
Umbreon I still think Tiara prince is the **** in this game)
Weight buff was not enough to turn Mewtwo into Snake and people are starting to figure out that taking ledge open Mewtwo up to take risks and lets that little window where he's vulnerable after a teleport be exploited. Scythe doesn't main Mewtwo but watching Rat go to work on his Mewtwo yesterday makes you even question M2K's assertion that Mewtwo destroys fast-fallers. He's also right about Mewtwo's tier placement, right around mid, closer to the upper end, but M2 doesn't dominate as hard as most people seem to think. It's a gut reaction to how good the teleport has become without stopping to consider its counterplay. Like Diddy nanners.
Sonic loses hard to a character that knows to play patient, not play his game and stuff his approaches well. He's slippery and his combos have combos but he struggles to finish about as much as ZSS does and his MUs aren't as consistent as they might appear as first glance. The build has finally settled and he's Sonic: Speed plus other things but not enough to be overwhelming or overly impressive.
Whereas Tink, Samus, Zamus, Peach, Ike, Zard, Chu can all be argued to things that either work for them in over 70% of their MUs or take the heat off in the bad ones. Tink is frankly not much worse than Link and Samus is frankly better than every character she shares her tier with and it's surprising to me that people don't see that. Samus CC, buffed with the crawl, Brawl Zair with Melee kit, improved smash missiles, improved FSmash range (minor but notable), stupid survivability, great keep away AND get-off-me options for a kit that really flows, without even talking about Ice mode ... Yeah, no, Samus is as underrated as Peach. (who still has a whole untapped meta of footstool DJCs + AGTs + I've never even seen a PM Peach DACUS out of a Dthrow even though Peach could keep doing Melee Peach things forever and still be good).
I know merging B/C sounds a little dumb but the game is that close honestly. I'm raising my eyebrows more at the split than if there was no split.
Frankly, kick Bowser, Ganon, Oli, Icies, Puff and maybe Weegee out since I can't get a handle on Weegee for the life of me and slice off the top 10 or so and you have the rest of the cast chillin in a single tier. It's that good right now. 3.02 could honestly be the last release and be the crown jewel of balance in Smash and fighting games.