The NetworkManager applet is a Gnome app. I'm running Siduction LXDE and network management is handled by the NetworkManager applet. I assume that the same applies for Siduction XFCE. I'm not sure, but I doubt it's used in Siduction KDE or Razor QT. One could find out for sure by browsing through the manifest file for the desired environment.
Another thing to think about if you use a personal VPN service is how easy it is to do the setup for whatever network management app is provided. I tried another Sid-based distro last year and if I remember correctly, you had to create text files containing the VPN info. I can't remember if the distro used Wicd or Ceni.
I use a VPN service that has multiple servers, so setting up text files for all of the servers would be a bit of a pain. Doing it in the NetworkManager applet is tedious enough.
05/09/2014-01 edit: I just checked the manifest for Siduction Xorg and Ceni is used in that environment. I've also thougt a little more about my statement regarding VPN configuration. Actually, a text file would be easier as you could easily duplicate existing files to create configurations for additional connectons and you could easily transfer those files to other Linux distros that you are using. This is assuming that Ceni can be configured for VPN service.