There should not be any difference in wifi performance between the two images. We only have the wifi driver as binary and do not have access to the source code.
WiFi issues are almost always interference related. Maybe the channel changed? Can you look at a wifi analyzer app using your smartphone to see that it's on an open channel?
@amitga The only thing we use over the B2B on our add-on boards is USB 2.0 and some GPIO. If you give us some idea of what you are trying to accomplish we may be able to offer some suggestions.