Bit torrent sync vs Rsync

[Hello_01]

What would be better to us bit torrent sync or Rsync (or anything else)
I would like to sync files across two free nas boxes in different locations.
When I upload a file to box A it uploads the file to box B as well as uploading a file to box B will also upload the file to box A.
Would it also be possible if I edit the file it only uploads the change to both NAS Boxes instead of re uploading the entire file to both.

 

[pirateghost]

Between 2 freenas boxes? Replication

 

[Robert Trevellyan]

Replication

When I upload a file to box A it uploads the file to box B as well as uploading a file to box B will also upload the file to box A.

It looks like OP wants 2-way sync, which is where BitTorrent Sync or Syncthing would make sense.