... see in redMany different views here. I might as well get my feet wet. 12-2 wire is rated for 20 amps and 10-2 wire is rated for 30 amps. 12-2 and 10-2 wire has black and white insulated wires and a bare copper neutral wire This is not a neutral wire, it is a safety ground wire. the white wire is the neutral, black is hot. 12-3 and 10-3 have black red and white insulated wires and a bare copper neutral wire. again, bare is safety ground The saw you are looking at is rated for 14 amps. The questions you asked were
(If I'm only using the outlet for the saw, and nothing else, can I just run 10 or 12/2 for the 5' run of wire?
Is there a reason I'd need to run a 12/10-3?
Do I need to swap out the 50A breakers?)
So... It is ok to run 12-2 wire to the outlet. IF the saw only requires 240 vac, and not 120/240 vac, then yes, a two wire cable is adequate. There is no need to run 12-3. Replace the 50 amp breakers with a 20 amp double pole breaker.