The 1917 has the first US military peep site, but has no adjustment for windage.
The 1903 has Mauser-type open sights.
The 1903A3 has an improved peep sight that has windage adjustments.
The 1917 is bigger and heavier - soaks up more recoil.
1917 has a forward/rearward safety on the right of the receiver, 1903 has left/right safety on the back of the bolt.
1917 has "ears" on the front site.
Both are awesome shooters that will go up in value.
The 1903 was the standard US rifle, but when the US got into WW1 in 1917, it was faster to convert the Remington Eddystone plant producing the British Pattern 14 (P14) to 30-06, so they produced the US Model of 1917.
Alvin York preferred the 1903, but shot a lot of Germans with the 1917 on the day he earned the CMH. The 1917 was used by more troops than the 1903 in WW1.