Nuance of using 仕事しなかったら or 仕事しなければ in this simple sentence?


I want to say " **It would be a waste if I do not have a job that does not
make use of my Japanese (ability).** "

However, I've no idea which of these options sounds native or what the nuance
of each option might be

(1) 日本語を生かす仕事しなかったら、もったいないよ。  
(2) 日本語を生かす仕事しなければ、もったいないよ。




The way you ended the sentence and the fact that you omitted を after 仕事
suggest that this is part of an informal conversation. しなければ sounds a bit too
formal in it, although it is perfectly fine in a more formal, especially
written sentence.

> 日本語を生かす仕事をしなければ、もったいないと思います。

しなかったら is OK in casual speech, but it could sound a bit dialectal and
certainly looks informal in writing. Certain regional dialects tend to use たら
more than れば. When I am speaking in Kansai-ben, I would probably say せんかったら
(if not せんと).

When I am speaking the standard variant of Japanese, I would most likely use
と.

> 日本語を生かす仕事しない **と** 、もったいないよ。

You get many more search results for
[しないともったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%84%E3%81%A8%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)
than for
[しなければもったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%91%E3%82%8C%E3%81%B0%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)
or
[しなかったらもったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%8B%E3%81%A3%E3%81%9F%E3%82%89%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)




The way you ended the sentence and the fact that you omitted を after 仕事
suggest that this is part of an informal conversation. しなければ sounds a bit too
formal in it, although it is perfectly fine in a more formal, especially
written sentence.

> 日本語を生かす仕事をしなければ、もったいないと思います。

しなかったら is OK in casual speech, but it could sound a bit dialectal and
certainly looks informal in writing. Certain regional dialects tend to use たら
more than れば. When I am speaking in Kansai-ben, I would probably say せんかったら
(if not せんと).

When I am speaking the standard variant of Japanese, I would most likely use
と.

> 日本語を生かす仕事しない **と** 、もったいないよ。

You get many more search results for
[しないともったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%84%E3%81%A8%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)
than for
[しなければもったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%91%E3%82%8C%E3%81%B0%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)
or
[しなかったらもったいない](https://www.google.com/search?client=safari&rls=en&q=%22%E3%81%97%E3%81%AA%E3%81%8B%E3%81%A3%E3%81%9F%E3%82%89%E3%82%82%E3%81%A3%E3%81%9F%E3%81%84%E3%81%AA%E3%81%84%22&ie=UTF-8&oe=UTF-8)

