Whilst perhaps I shouldn't vote on this as a predominately non-nationals shooter, I voted for the 40 because it would possibly be enough to sway me towards shooting further afield.
It's very rare that an open or CSFTA club shoot won't either have 40 targets or other styles of comp to make a ful day of the event. If I'm going to drive up to 80 odd miles, I want more than 30 shots.
As regards to practicality, rather than putting out more targets, I'd go for the two pegs per target per lane option which would make course building quicker and as long as the pegs are put out with some thought, then it won't be the same shot twice. The downside to this would be the number of shooters on the course would be reduced unless having say 3 per lane.
If the one target one peg format is followed, then would it really add that much more time on to the session.
Regardless of eventual format, I'd say that 40 shots makes more economic sense to the average shooter.