Tan,
SC7 is a server, so its clients (Jive remote, Duet receiver, SB3) access it directly. The Jive wifi remote controls the SC7 server, not the SB3. So if the wifi signal gets weak, you will lose control of the SB even when you are standing right near it. The SB3's IR remote communicates directly with the SB, so a few layers of communication are removed and speed and reliability are better. If you are losing wifi signal in next room, you may need to upgrade your wireless access point to something with better signal strength. Maybe you have an older model? You can check wireless signal strength somewhere in the menu of the remote.
Duet system is still buggy. I hope it will continue to improve over time with updates. It is NOT as reliable or fast as SB3 w/ slim 6.5.4- yet.
Rich