performance. sshfs is dog slow compared to NFS on a local network.
Also, coherence: sshfs manages to hide a lot of the ugly details, but you'll meet coherence problems on sshfs much more often than on nfs. They both do aggressive caching, but nfs gets help from the server side and is thus usually better.
Both good reasons. My personal use case happens to make these issues unimportant: mounting remote file stores that are only accessed by me. But I guess for mulitply-accessed files on the local network, nfs headaches may be worth the trouble.
I'd started using ssfs for something and found this slowness issue. I asked my mentor about what could be done to improve it, and he said "If you're using sshfs, you've already lost".
'scp' is very slow as well. Anything bigger than a small text file gets rsync'd. Small text files get scp'd, because remembering rsync flags is a minor annoyance :)
