saved blobs using Ifaith but what about IPSW??

I saved my 4.3.3 blobs using Ifaith on my wifes windows machine. It also gives the option to have signed IPSW, but not sure if needing to do this?? I am currently jailbroken but wondering if this completely restores the phone when creating using Ifaith. Anyone know the benifit of creating IPSW along with blobs or can I still downgrade later with just the blobs saved for 4.3.3 without creating a signed IPSW