34's are better offroading than 33's. But 35's are better than 34's so why not put 35's on? Get my point? Unfortunately 4Runner's were never built for large tires like Jeeps. A 4Runner will never be able to do what a Jeep can do off-road. It is what it is. I think a lot of people put 34's on their 4Runners and that should be fine if you re-gear, but to me if you want big giant tires and rock crawling ability, get a Jeep JL. I think you can put 35" tires on it without any modifications. I am sure also many are running 34's without re-gearing, but I wonder what it will do in the long term to the transmission.

Yep. I've run both sizes. On a trail like the Rubicon or similar - something around a 6 out of 10 on the difficulty ratings, the larger tire starts to make a meaningful difference on some obstacles. A little extra lift height also helps in that situation.

There is a noticeable difference in net gearing each time you jump up in tire size. The 34" tire is roughly the same jump in size as compared to a 32.8" tire as the 32.8" tire is from the OEM 31.6" tire. I have not found any issues with gear hunting being worse on the 34" tire than either of the others. If anything it may actually be better because it doesn't down shift as often.

What I did find was that 4.56 gears ended up being significantly worse in terms of highway mpg to the point that I removed them. I had a few issues with ARB front locker so that was also a side issue with the gearing swap frustrations. My last highway trip towing my small teardrop camper with 4.56 I got 11.7mpg IIRC. That was worse than I got with OEM 3.73 diffs by a significant margin. Two weeks ago I towed the same camper on a similar trip and I got 14.5mpg. That means I'm burning about 25% less fuel per mile. That's a significant difference in terms of engine load and efficiency. The reason is that 4.56 gears are not deep enough to stay in 5th gear in either situation and 4th gear works either way.

Unloaded on my last road trip with 33.0" tires (275/60/20) I got a dash reading of 18.7mpg over 300 miles in the mountains at highway speeds. From Salt Lake City Utah to Garden City Utah. I drive that trip frequently. With the 4.56 gears and no trailer I was getting 15mpg or less. Again - significant reduction in engine load/efficiency with the OEM gears.

My logic was that if I'm going to get 14-15mpg - I'm just going to swap platforms to something that should get 14mpg (an LC200 or LX570) or even a Tundra and at least have 400hp to go with my 14mpg. I really wish we had the 6AT and then you could run 4.88 or so diffs and still have good highway cruising rpm range.

Of course stock tires were the best by far in every scenario except offroad ground clearance. For highway driving - stock tire size is the way to go. It's not really even close. The next set of highway tires I buy will probably be a downsize to something around stock height. I keep two sets of wheels/tires and swap them around depending on what I'm doing. I have a large garage, so storage is no problem and it takes about 10 minutes to swap them over. If I could swap diffs in 15 minutes - I'd probably swap the 4.56 in for offroad trips. There's just not a great solution that's ideal for everything. So we have to find some sort of balance that works.