Depending on what pigtails you use, I find they stay in as well as the rebar to normal depths. I feel pigtails are less likely to short out than rebar since the screw on rebar insulators tend to come loose.  I use mostly Gallagher pigtails but these from Premier are very good also. The shorter one works well in most summer situations with some calves in the herd.  The taller one clears stalks and snow and is useful as long as you don't have small calves in the group that will go under it.

I only use rebar when the ground is frozen on the surface and I need to hammer them in. Single steel tee posts work for temporary corners. I add a Speed Brace t post brace for semi permament ends and corners.

As far as wire I have very good luck using 14 gage aluminum wire on reels for frequently moved temp fences.  The aluminum is stronger and doesn't stretch (and droop) as much as the poly I tried. Aluminum wire is much lighter to carry around and wind up on reels than steel.

Jim