Difference between duìbùqǐ and duìbuqǐ
This is only a pronunciation variation in spoken Chinese. Most untrained Chinese people may not even notice the difference between them.

There is no difference between the two variations in your examples.

It's like asking what is the difference between "I'm going to do ..." and "I'm gonna do ...".

Note: There are word that would carry different meaning using neutral tone or not. E.g, 东西 means "east and west" when pronounced as "dōngxī" (without neutral tone), and means "thing" when pronounced as "dōngxi" (with neutral tone).
In a dictionary, a word that must be pronounced with a neutral tone will be explicitly noted with a neutral tone.