The MacBook Pro Early 2015 Retina has an 802.11n WiFi standard which is better than most laptops that were launched around the same time as it. Most comparable spec notebook PCs that came out around the same time as it have an 802.11a WiFi standard. This notebook PC also have 802.11ac and 802.11b and 802.11g WiFi standards.
An 802.11n WiFi standard is actually the best Wi-Fi standard across all MacBooks that have been on the market for a similar time to the MacBook Pro Early 2015 Retina.
Across comparable types of portable PC the worst Wi-Fi standard is 802.11a.