The iPhone 4S supports a 2.4 GHz 802.11n band and it works on speeds that are half those of the iPhone 5.
The differences aren’t very noticeable regarding the capacity for surfing on the net.
However, in terms of the synchronization of the devices via Wi-Fi things change as this will be possible at speeds double those you were used to until now.
Routers that are compatible with the 5 GHz 802.11n standard are necessary for this.
Check out the video below.