A: Can you give me a pen?
B: Yes, take it.
A: Thanks much OR Thanks a lot
Is there any difference between these two phrases? Which one is preferred to use?
Thanks a lot is the ordinary use in conversation, or bare thanks! Many thanks is more frequent in writing, particularly in formal writing. Thanks much is unusual.
Here's a Google NGram. Keep in mind that the underlying corpus here is printed works, so the more formal phrase is significantly overrepresented.
In my experience (U.S. English; Indiana, Kentucky, Tennessee and Florida) "Thanks much" is a quick informal expression similar to "Thanks!" On the other hand, "Thanks a lot" would be taken as sarcasm unless context and the tone of voice made it very clear that it was sincere. Better to avoid "Thanks a lot" unless you intend to be sarcastic.