I agree with ironraven.

Bolt cutters are too heavy, and too much of a break-and-enter type tool. Both landowners and law enforcement may well take a dim view of someone carrying and using these.

I suspect that in a genuine long-term emergency, cutting a landowner's fence is an invitation to the "bullet dance." Most people who cut fences are up to no good.

That said, a Leatherman will go through two-strand barbed wire nicely. But the tool I would choose is a genuine Vise-Grip. They have a wire cutter that will go through any wire I've encountered -- even hardened wire. The 5" is light and handy, but a 7" gives much better leverage, and the 10" is the chairman of the board. Easy to justify carrying them, to yourself and others, since they have so many uses off the grid. I wouldn't be without one.