what's the difference between these two expressions, is ther a difference?

This is no big deal.
This is not a big deal.

 

i think that there is no difference between them , but it depend on how you are going to use them. like in these situations:
A son making a confession to his mother : I'm the one who broke the window last year !
The mother : it's okay ! it's not a big deal.

in another situation:
a wife to her husband: do you prefer me to cook the dinner tonight or shall i ask the maid to cook it ?
the husband : there is no a big deal whether you gonna cook the dinner or the housemaid .

in both situation they have the same meaning that it's "not important"

 

"There is no big deal whether you gonna cook dinner or the housemaid."
It would be a seriously big deal to the housemaid!
Anyway she'd probably be tough and hard to chew!

 

"No big deal" tends to be used on its own:
- Sorry I can't go to the movie with you tonight.
- Don't worry. (It's) no big deal.

I've never heard "there is no big deal whether..." and that construction sounds very odd to me!

Elizabeth