What exact make/model do you have in mind?
Repeaters connect back to the router via the router's Wi-Fi, whereas an extender connects back via Ethernet cable or powerline technology to a LAN port on the router. The repeater needs to be sited in a good position to receive a decent WiFi signal from the router, which may mean it still cannot reach the area you require. In addition to this, the repeater broadcasts out a fresh copy of the Wi-Fi signal in all directions, including back to the router. A repeater normally uses the same Wi-Fi channel as the router and this can cause the router's Wi-Fi signal to be cancelled out, leaving the repeater with no connection to the router. In addition to this, a repeater can cut your download & upload speeds by 50%, because the repeater has to serve both the router and the device.
Therefore a much better approach is to use a true Extender. These are often available in a kit of two units that connect over your electricity, back to the router. However, you may have problems with this sort of scenario if the two units are connected to different electrical ring main circuits. Some people have issues like this & others do not, so it is impossible for me to predict if this will be OK for you.
