What is the difference between 7 dBi and 10 dBi WiFi router antenna for 5.8 GHz?
The 10dBi antenna will increase the range by about 1.4X in free space, provided the antennas are polarized and aligned correctly.  The 7dBi will be more forgiving of misalignments.  For a typical WiFi setup, where portable users are generally unaware of their antenna location or orientation, and in some cases even the router's location, I'd choose the 7dBi for its wider angle.