Spi pros: faster, easier code (not sure)
Cons: uses more pins (3 + n devices)
I2C pros: uses just 2 pins with any number of devices.
Cons: slower, more complex code.
For that antenna, unless you are connecting many antennas to one arduino (which i dont think is necesarry because they can work as a mesh network right?), just go for spi.
For my application I will have a central unit with an NRF24L01+ transceiver and several sensors, each with an NRF24L01+ transceiver.
The central unit will log the inputs transmitted by the sensors.
If I can get it working, I will use the network layer of the RF24 library to extend range.