On my runner I have had 255, 285 and 305.
255 was a BFG KM2. Great tire that handled everything exceptionally well except snow and ice, it was horrible in the snow. It was very loud on the road and wasn't the best for anything other than driving in a straight line. That doesn't have anything to do with the width though...
285 is my current size, and is a Cooper A/T Maxx, an aggressive all terrain tire with nice road manners. Handles the elements well too and you don't get that jerky feeling when traveling through small puddles or mud holes at speed on or off road, and still maintains it street-ability. Weight is a little closer to the 255 depending on the tire you get.
305 was a Goodyear Duratrac, another aggressive all terrain tire. This width was my least favorite. Lots of drag on the road and felt a bit more sluggish. Did ok off road but seemed to be too wide for the 4runner. Cruising at any speed above 10 mph and you can expect the tire to grab every puddle and mud hole and rock and whip you in that direction rather than cut through it like the other sizes. It may be ok for snow and deep sand or mud, but everything else I didn't like, and the other tires were more than capable of handling.
Overall my favorite size so far is the 285. For our vehicles it seems to be the perfect compromise for road manners, off road ability, and weight, while still keeping a common tire size with great availability and options. Pretty much everyone makes a 285 tire in every style and flavor you could want.
Just my opinion. If they had more options and affordability for 255 tires I would probably have 255 tires right now, but seeing as options are limited and can be pricey, 285 is my current favorite.