IMO the Hummer will get stuck in sand.
As mentioned earlier, there is sand and there is sand.
There is packed sand such as at Daytona where cars used to race on it (and you can still drive on it, with ANY car) is one kind of sand.
Now go to a fine sand beach, like here in Ft Myers Beach, where we have "sugar sand", and yes, the Murano will likely get stuck. So will the highlander and the pilot. All with OEM tires of course.
What about that Hummer?
Yep.
You put the tires from a Murano on it and it would no doubt get stuck.
If you are going out to play in the sand and the mud, you need chugger tires. Street tires won't make it and it has nothing to do with the car.
Any 4wd, even a jeep wrangler, could get stuck in the sand if you use nice smooth highway tires and the sand is nice deep soft sand.
I think Fire trails "might" be a problem also.
Again there are fire trails and there are fire trails. The ones I am used to in the NJ pines and FL wilderness are on sandy soil that ruts a good bit leaving a high crown in places.
The Murano does not have good clearance under the car and as a matter of fact, you are not going to hit a skid plate on a high crowned fire road. You are going to tear off a transmission cooling chute or a muffler.
Homer