It depends what your after as to how you may set the barrel.
For example my side by side is set at 1/4 and 3/4
The reason...
Open (or cylinder /skeet) suggests that there is nor restriction from the chokes; suitable for quarry close up offering maximum spread ( which will minimise damage up close). Open is no good at further distances however because it has already spread, therefore you would require a tighter pattern for longer distances.
So full choke offers the tighest choke must suitable for longer distances, keeping the pattern tight, concentrating the spread for a more ef