I have used Norton for decades and Identity Safe since it came out. Changed from IE to Firefox over a year ago and was happy to find this interface to Identity Safe. If you like Identity Safe w/ IE and choose to move up to Firefox, this is definitely a no-brainer.
I know this review is not specific, nor does it identify differences. I worked in IT for 35 years, mostly with IE. The last few years I changed all of my home machines to Firefox to improve up-time and have been extremely pleased. It took me a bit to figure out the way Firefox works with Identity Safe (vs IE) and that is the only down-side I noticed.