The higher price of the Sauer 100 is worth the extra money, the Sauer trigger and I believe the safety is metal and the trigger guard like mentioned. I like synthetic stock in the Sauer better then the m18 and the beach is nice tho I'd pay more for walnut. I like the bolt knob better on the m18 and tho the trigger is polymer it is incredibly stiff, I've seen metal trigger flex more. I had to take the m18 apart to confirm the safety lever was plastic because it's hard to tell, again it's very ridged.
the U.S. Market m18 and sauer 100 have screw on barrels and look pretty easy to have one make up, the other market guns are pressfit/ thermal locked in.