これで決定 vs これに決めた


Having figured out what to do, the protagonist says「これで決定」. Later, having
picked one option out of several, she says 「これに決めた」.

What's the difference in the meaning between these, and why are the particles
different (で / に)?




I think these two これs are referring to different things.

In **これで** 決定, これ is referring to the current situation (i.e. what just
happened) so a translation would be "and with this/because of this, I have
decided". This これ is not talking about **what** was decided. [See this
link](https://japanese.stackexchange.com/questions/25698/what-is-
the-%E3%81%93%E3%82%8C%E3%81%A7-in-%E3%81%93%E3%82%8C%E3%81%A7%E5%A4%B1%E7%A4%BC%E3%81%97%E3%81%BE%E3%81%99).

In これ **に** 決めた, これ **is** talking about what was decided. "I decided **on**
this".




I think these two これs are referring to different things.

In **これで** 決定, これ is referring to the current situation (i.e. what just
happened) so a translation would be "and with this/because of this, I have
decided". This これ is not talking about **what** was decided. [See this
link](https://japanese.stackexchange.com/questions/25698/what-is-
the-%E3%81%93%E3%82%8C%E3%81%A7-in-%E3%81%93%E3%82%8C%E3%81%A7%E5%A4%B1%E7%A4%BC%E3%81%97%E3%81%BE%E3%81%99).

In これ **に** 決めた, これ **is** talking about what was decided. "I decided **on**
this".

