Depth of field question

Thank you for the responses. I only have two primes which share the same focal length; Nikkor 105mm f/2.5 AIS and Nikkor AF-S VR micro 105mm f/2.8G. I never tested them carefully against each other but I am always left with the impression that the VR gives me more depth of field. Perhaps that has to do with their bokeh variation, the inferior one emphasizing more clearly the departure from the focus zone, making it seem smaller.

Haim