VNC on one computer, not on the other

This seems odd to me. Both of my computer have WIndows 7 64-bit. One one, I was given the option of RDP or VNC, so I chose RDP (Windows setup, I think it was called). On the other computer I wasn't given the RDP option, only VNC. Why is that? I connect okay to both, just curious about why this happened (I uninstalled and reinstalled to see if I could change it but couldn't).