SS

Pros:

> Fast to type

> Follows other nomenclatures

Cons:

> May be confused with SoulSilver

> Cannot differentiate game from game

SwSh

Pros:

> Easy to recognize
> Unique
> You can say 'swish' (which is similar to Switch so that's a good thing), or 'swoosh!'

Cons:

> Breaks the nomenclature with former games
SnS

Pros:

> Easy to recognize

Cons:

> Breaks the nomenclature with former games

Small problem:

> Takes longer to type if you are using a PC

S&S

Pros:

> Easy to recognize

Cons:

> Breaks the nomenclature with former games
> Harder to type
> Some apps and search engines can bug with the '&'