Ok here are my impressions. My 930 and my 940 are very similiar. Trigger groups are essentially te same although the 940 has plated parts in it. Magazine tube on the 940 is plated and has a 9 rd extension 930 is not plated. Both come with 3 chokes but te 940 has briley extended chokes 930 has standard tubes. 940 chokes are M\IC\C and te 930 has I\M\F. The receivers are different the 940 has a massive loading port and the 930 does not shell elevator is also different. On the 940 barrel the gas tube is different it has scallops in it. The gas pistons are also different te 930 has the 2 rings that sit on each other. The 940 piston is a 2 ring design only the outer one is now removeable. There are also scallops in it.. so my impressions is the 940 worth it YES.
To make my 930 run the way a 940 does here is what it cost
Or3gun duck hunting spacer tube and other parts $175
OR3GUN piston $40
Mossberg 930 $500
Extended choke tubes $100
$815 total and I do not have the plated mag tube and trigger.
I do not have the Mag extension
Or the oversize bolt handle.
My 940 was $900 with all the machining and every good you could want.
I am going to make a video about this because I cannot get the pics small enough with good resolution.