The core difference between blossom and NIP-96 is the focus on re-uploading files

If we want censorship resistant media then we need to be able to re-uploaded the files to other servers. similar to now nostr events get spread around the network

NIP-96 could support re-uploading files but it isn't currently part of the nip

There is also the difference that NIP-96 has a "/.well-known/nostr/nip96.json" file and customizable endpoints. In my view this is not a feature and makes it much more difficult to work with servers since clients must first fetch a map of the endpoints before they can talk to the server.

Blossom however requires blobs be served from the root of the domain ( example.com/.ext ) while this isn't very friendly to server admins it makes things very simple and easy to understand.

Also searching for a missing blob is a simple as replacing the domain. something a user could easily do ( and understand ) in the browser address bar

There are more smaller differences but in my view these are the major ones