If by “best” you mean the most remote a.k.a. convenient way for a locker user to unlock his/her locker, that would be a mobile app, which operates as a locker “key” via Wi-Fi of mobile network. A smart locker with such smart locker keys via wi-fi, can be basically unlocked from anywhere the locker user wants to (you could unlock your office locker from the exotic vacation half way around the world, if you need to).
With such wi-fi unlocking, an RFID reader is not required to unlock the lockers. Such truly mobile smart locker solution saves you money (no RFID readers). Sometimes even more importantly, it enables the fully clean-line visual appearance of locker doors and the locker bank. Something you and especially your workplace interior designer can appreciate when refurbishing your office space.
The second best option, range-wise, is via Bluetooth, whereby lockers can be unlocked with a mobile app, via Bluetooth, when users are within range of the Bluetooth signal from the reader on the locker bank (up to 10 meters/30 feet away, depending on the strength of the BT signal).
NFC (Near Field Communication) doesn’t really provide “remote” locker usage as users have to be within 1- 4cm from a reader, which is basically the same as with normal RFID cards. It does take away the necessity to have a card on you, to unlock your locker (that rarely happens with your mobile phone, right?)
Also, wi-fi, mobile network and Bluetooth technologies are all included in every new smartphone on the market today, which isn’t always the case with NFC.