Okay I know it's 1", but what are the advantages and disadvantages of both?
I am a little concerned when the vehicle gets loaded with weight that the 2" may not be enough. I plan on putting a roof top tent on top that weighs 120 lbs. and other camping gear in the back. How much sag is there when you put on a lift kit?
Ok. Pissing test over? Can we get back to the orginal topic now?
To answer the OPs question....
3" is about the max you can go on a 4Runner before you start running into issues with the CV axles binding. Some people say 2, but I can tell you, in MY experience, 3 is where it's at.
NOW, the questions for you are as follows:
1) what size tires do you plan on running?
2) What else is going to be in the 4Runner, besides the RTT?
3) Are you running an aftermarket roof rack, or the stock one?
I ask these questions for a few reasons.
Size tires makes a difference in clearance. I can tell you, I'm running 35s, 35x12.5 to be exact, with a 1.5" body lift, a 3" suspension lift, and 3/4" of my fenders cut. I also took a BFH to the pinch weld and the firewall, and have no problems rubbing. I'm also running 1.5" Spidertrax wheel spacers, because I was ON the UCA.
The ammonut of weight you're going to have in the back of your 4Runner, as well as on top, is going to make your truck sag. Ad to the fact you MIGHT be planning on an aftermarket rear bumper, with or without a swing out, as well as a fullsize spare, and that factors even MORE weight in.
The stock roof rack isn't made to handle the weight of a RTT. At least not with people sleeping in it. I would look at a sleeping platform for the back of the truck, or maybe a expo style trailer, or little camper.
Unless you plan on going with an aftermarket rack, which in that case, you'll be alright.
IOT decide which lift to get, you NEED to know all this stuff. You need to have it all figured out.
You can get anywhere from soft, to heavy duty springs, and struts, and the amount of weight, tires, ect is going to factor into what you should get.
What kid of wheeling do you plan on doing? Expo? Rock Crawling? High speed desert stuff?
These questions need to be answered as well, as getting the right set up would be dependant on ALL the above questions.