Genetive plural (-sten/-sien)

[decyferbrown]

Terve.

I am steadily working through the grammar topics on uusikielemme, and I am currently on the chapter concerning the genetive plural.
Now, it says for words ending in '-e' either '-iden' or '-itten' can be added (eg. kirje -> kirjeiden/kirjeitten) and that, although they both mean 'of the letters', the
'-iden' ending is preferred and most commonly found to be used.

It then goes on to say that words ending in '-nen' replace the '-nen' with either '-sten' or '-sien', (eg. nainen -> naisten/naisien), both meaning 'of the women'.

What I wanted to know is, which of the '-sten/-sien' endings is more common in the spoken language, and why?
Is one of a more formal register, or are they both acceptable in formal, informal and slang circumstances?

I hope someone can answer this, preferably a native speaker, and thank you for taking the time to read my question.

[Jukka Aho]

It then goes on to say that words ending in '-nen' replace the '-nen' with either '-sten' or '-sien', (eg. nainen -> naisten/naisien), both meaning 'of the women'.

What I wanted to know is, which of the '-sten/-sien' endings is more common in the spoken language, and why?
Is one of a more formal register, or are they both acceptable in formal, informal and slang circumstances?

They’re interchangeable, there’s no difference in register or meaning.

It seems people prefer one over the other, though... (see the number of hits)

• naisten vs. naisien
• miesten vs. miehien
• lasten vs. lapsien

My theory is this is because nais-ten, mies-ten and las-ten only have two syllables each whereas nai-si-en, mie-hi-en and lap-si-en require three. Simpler variant wins!

[decyferbrown]

Thanks very much for that!!
Was a bit puzzled about that and didn't want to go around using the wrong form, offending innocent old women with the informal usage and such!