As the question says. There's a lot of threads around on NFS vs. Samba/SMB, but a lot of them are outdated or refer to old security models, or just give a one-line "use SMB with Windows".
Both modern Windows clients and modern *nix file servers can handle both of NFS or SMB/Samba. Whichever protocol is chosen, one will be using a "native" protocol and the other won't. So in mixed environments (*nix server/Windows clients) it's not as simple as "for X use Y".
So I'm interested in actual pros, cons and experience. The few threads I can find that cover modern incarnations of these protocols suggest as possible differences:
Threading? - Samba is single threaded (for example FreeNAS forum posts suggest that a single core at higher speed is better than multi-core for Samba serving Windows clients, for this reason). So presumably during congested periods or with high or complex levels of demand or locking/unlocking activity, this might be a factor;
Single file performance? - some threads suggest NFS is more efficient or serves faster with smaller files <= a few MB (which is many/most of them?) and comparable for larger files.
Security? - some threads suggest that NFS doesn't implement as effective a security model as SMB, or at least hasn't historically.
What's the current state of play on this for a modern *nix file server with Windows 8.1/10 x64 clients, if NFS is also enabled on the clients?
CIFS support is not that great on some UNIX. AIX crashes like this come to mind but it also isn't great at POSIX for *nix clients like some apps expect.
Some NAS appliances can export the same shares as NFS and CIFS. Your assumption that you must pick one is not necessarily true.