[Samba] Samba 4 Alpha 17 to 4.0.x update - questions concerning S3FS / NTVFS

[X-Dimension]

We had used Samba 4 alpha 17 for a long time and want to update our 
server now to Samba 4.0.x.
The old Samba versions was using NTVFS and Samba 4.0.x is now using S3FS 
by default.

So, what is the best practice now? Should we stay on NTVFS or should we 
switch to S3FS?

The global part of our smb.conf looks like this:

---
[global]
         interfaces = eth0
         netbios name = PDC
         passdb backend = samba4
         realm = MYDOMAIN.LAN
         # Global parameters
         server role = domain controller
         server string = PDC
         workgroup = MYDOMAIN
---

When we start Samba 4.0.x with this configuration, is it using NTVFS 
like before or is it using S3FS then?

Thx for help!