Hi George,

In general moving from a SAN to NAS will affect the performance at a certain point depending on the scale of your project. There are a lot of additional considerations you might want to take into account such as how users are interacting with the information and the configurations involved from one system to the next. 

Given these additional specifics, I would recommend you perform a small test prior to implementing the transition.  For best practices, monitoring file transfers at the individual byte level and keeping an accurate file count from the starting folder to the destination folder will allow you to compare and contrast the differences and determine what system will suite your needs.