Re: Mii Brawler switching specials to gain advantages in different matchups. I missed the discussion but I have a lot of experience playing the character in all different sizes and using different specials. The following applies to mid height/weight, which is the standard ruling in more places (not all!).
Switching between helicopter kick and piston punch is more impactful than between the neutral-bs. Uppercut is generally better for two main reasons.
1. Uppercut gives Brawler another kill option in a kit with few kill options. Shot put gives you a pretty telegraphed damage-racking projectile in a kit that doesn't have problems racking up damage anyways.
2. In general, while playing Brawler you have to be extremely delicate in the way you setup the opponents' HP for early kills, and shot put's high damage disrupts your ability to do this. At Shot put's usable percents, uppercut becomes a kill move.
-From 0-20~% you have dthrow->fair chain grabs that end in upb. At 0%, Shot put is a tool you can't use effectively in neutral. Grabs and attacks that lead into grabs have much better risk:reward at these percents.
-From 30-40% it's important that you try to set up into the killing dthrow->upb combo. Hitting an opponent with Shot put just ruins your chances of landing the grab via setups.
-From ~40-45%, you have the death combo of dthrow->helicopter kick. If you haven't set up into the grab via nair, general juggling, etc then you have to either fish for the grab by the ledge or accept that you probably won't kill until much higher percents.
There's just little room for Shot put (15%) to be useful until past kill-combo percents. If you get them past the percents where you can't combo into upb, it's likely you won't be killing for another 100%. It's similar to Melee Marth in that way- Smash4 Sheik too, I suppose.
In short, your ability to kill with helicopter kick in particular hinges on the ability to grab the opponent at the right spot at the perfect percent, while also setting up your early combos in such a way that the opponent ends up in that spot as well. Shot put impedes this until higher percents where uppercut becomes a viable kill option.
Piston punch is another great killing upb (which is arguably better overall) which gives you some pseudo 50:50 kills at low kill percents as far as common kill moves go, and is effective at a much wider spread of percents than helicopter kick. The upward traveling hitbox is much more useful in catching airdodges against characters you'd combo more vertically too, so that's another area it differentiates itself.
