Less difficult if the hill is really steep because if it's really steep, you lose traction on a standard bike and your rear wheel spins out. I bike a trail out at Yankee Springs in Michigan. There's one hill that's so long and steep that unless you go into it with maximum speed, which is difficult because it comes right after a quite technical stretch of single track, then around half or three quarters of the way up, your rear wheel starts spinning instead of getting you up the hill and you start backsliding.
That said, I'd never get those ridiculous tires. Sure, on something like that, they may help you out, but the entire rest of the time you're riding with those fat tires under low pressure, you're dogging it. You get no speed. And you say you don't care about that, but you need it. You need to be able to be dynamic in your riding, to be able to slow or stop abruptly and to be able to accelerate quickly and hit high levels of speed, because at Yankee Springs, it's a far better ride to know the trail and know you need to explode out of that technical bit of single track and make it all the way up that hill by going fast and hard while others in the field who don't backslide.
Aside from the fact that the benefits are somewhat dubious and are enormously outweighed, literally, by the cons, plus-size just looks straight-up ridiculous.
Here's what you do to see if you'd like plus-size: on your current standard mountain bike, let the air pressure out of your tires so that you're only running on, say, 25psi, just enough that you're not dinging your rims hitting bumps. Then ride. That ride, that will be akin to plus-size, except plus-size will even be slower and doggier.