RPi 2/3 if I'm not wrong are around 3 Watts (fanless) An old P4... For sure it's not lower than 60 Watts power consumption
And if he wants to run only a Tor relay, advantage to have Windows OS is relative ;) Not really agree...
But agree about cpu speed ;) I don't remember, RPi v3 has the famous AES-NI that make everything faster for Tor ? :s
17/10/2016 14:18, Neel Chauhan :
The disadvantage of the PC approach is space and higher power consumption, but the advantage is that you can use *BSD and Windows, and can possibly take advantage of faster speeds.