What is the difference between 「もらいませんか」 and 「もらいましょうか」?


I came across this fill-in-the-blanks question in a reviewer:

> にもつ、＿＿＿＿＿ か。

The choices are もらいません or もらいましょう.

My current understanding is that もらいませんか is of the form V-ませんか which
translates to "why don't we/I V?", while もらいましょう is of the form V-ましょうか which
translates to "shall we/I V?".

If I use もらいません, then it would mean "Why don't I receive your/that luggage?".  
If I use もらいましょう, then it would mean "Shall I receive your/that luggage?".

The correct answer was もらいましょう.

But don't they both mean the same thing?  
What is the difference between the two and when to prefer one over the other?




I guess ～ませんか and ～ましょうか are sometimes taught as being two similar ways to
make a polite suggestion.

Indeed, they can be used with a somewhat similar meaning, for example in

> 行きませんか _vs_ 行きましょうか

when the context suggests

> why don't we go (together)? / would you like to go (together)? / shall we go
> (together)?

In fact, the two constructions actually mean something completely different:

  * V + ～ませんか is asking (politely) if **the other person** might want to do V

  * V + ～ましょうか is _offering_ (politely) that **you** do V.

Indeed, the context could suggest translating

> 行きませんか  
>  why don't you go (without me)?
>
> 行きましょうか  
>  shall I go (instead of you)?

Of course, for your example, ～ましょうか should be the natural choice:

> にもつ、もらいましょうか  
>  shall **I** take the luggage?
>
> にもつ、もらいませんか  
>  why don't **you** take the luggage?




I guess ～ませんか and ～ましょうか are sometimes taught as being two similar ways to
make a polite suggestion.

Indeed, they can be used with a somewhat similar meaning, for example in

> 行きませんか _vs_ 行きましょうか

when the context suggests

> why don't we go (together)? / would you like to go (together)? / shall we go
> (together)?

In fact, the two constructions actually mean something completely different:

  * V + ～ませんか is asking (politely) if **the other person** might want to do V

  * V + ～ましょうか is _offering_ (politely) that **you** do V.

Indeed, the context could suggest translating

> 行きませんか  
>  why don't you go (without me)?
>
> 行きましょうか  
>  shall I go (instead of you)?

Of course, for your example, ～ましょうか should be the natural choice:

> にもつ、もらいましょうか  
>  shall **I** take the luggage?
>
> にもつ、もらいませんか  
>  why don't **you** take the luggage?

