Well there's the obvious -- shorter is easier for the stock, or dogs or coyotes, to go over if they want to. So shorter is more appropriate in situations where nobody is going to be highly motivated TO go over, and/or where it doesn't hugely matter if stock goes over (e.g. subdividing a field that has GOOD perimeter fencing)
The shorter electronet you can just step over (being careful of your crotchal regions as you do it
) whereas the taller stuff you really need to unhook the electric supply and/or have a 'gate' (e.g. where rolls join) to get thru without getting you zapped.
The big issue to me is WIND. Because I live on a pretty windy property. I find the stuff I have, I forget if it is 45" or what but it's Premier's taller poultry electronet, is really really inclined to blow over (or just blow around to the point that sag develops and grounds the fence out too much for the charger). So I will be ordering a roll or two of the sheep stuff next spring and it will be the SHORTER stuff, what is it, 35"? So as to have less wind stress on the posts. OTOH if you live in a real sheltered location, that is probably not an issue.
I really like the stuff btw (I only have the poultry net, which has many more verticals and a few more horizontals than the sheep/goat type net, but is otherwise basically the same and I *use* it mostly for the sheep). It really really IS as quick to set up and move as they say it is, providing you follow the directions (DO NOT ROLL IT UP, just fold into a drapey pleat from each post). However you also really really DO need to keep under the fenceline extremely mown-down, particularly if you do not have the most massive charger in the world; because even with the fence set up as tight as you can get it and all corners tied back to supplemental posts, it takes only the most *minor* amount of sag to put the bottommost charged strand on the ground.
Good luck, have fun,
Pat
