I currently use SMB-3. The reason for this is that SMB3 has some very distinct advantages over 2 and 1 and is backwards compatible. If you do a google search on SMB3 you will find plenty of information. I have had no problems with file access either locally or remotely while using SMB3.
I had done some digging on this months ago but don’t remember the details anymore. All I doremember is that unless you have Win 8, you can’t take advantage of the improvements in SMB3, and are best off in SMB2 for Win 7. So I use SMB2 on mine.