its not really a matter of opinion actually there are specific advantages and disadvantages to each of the four options.
First off let me start with a brief explanation of the stock suspension on the rear of the 3rd gen 4runner. The solid rear axle is linked to the frame using 4 links in line with the frame and 1 link perpendicularly aligned with the frame. the two lower links are angles in slightly, and the two upper links angled in more than the lower links, but are not fully triangulated. Because the upper links are not fully triangulated a flat pan hard bar is used to center the axle left and right.
side note: an advantage of this 5 link setup is that the links dont require very much rotation or misalignment with close to stock travel numbers so rubber bushings can be used for quite some time without having to be replaced.
When the panhard bar is flat the left to right movement is small compared to the up and down movement. On a non lifted truck the axle is compressed from ride height, it slowly moves towards the passenger side, as it extends it slowly moves towards the passenger side.
When you lift the truck, the axle moves down from the body and all of the links angle down, including the panhard bar. The further down the panhard bar is angled the more left and right movement you attain from up and down movement. This causes the axle to move to the passenger side when the truck sits at the new lifted ride height. Now when the axle is compressed from the new ride height it first moves to the drivers side, then as the axle extends downwards it moves more quickly towards the passenger side.
Do nothing:
Advantages: Its free, and the axle will center it self correctly when flexed out or fully bumped.
Disadvantages: The axle will not be centered at ride height. There will be more sided to side movement than there is if the bar is flat. The more lift you have the more severe the disadvantages. The roll center only rises half of how much the truck is lifted, this nets more body roll.
Adjustable panhard:
Advantages: Centers the axle and corrects the left to right pinion angle. It is adjustable for different lifts.
Disadvantages: The axle will not center properly under full bump and flex and will cause more of a problem with the drive shaft running into the gas tank(this can be fixed by adding extended bump stops). all of the disadvantages of doing nothing except the axle being centered. It is the most expensive option.
Panhard drop bracket:
Advantages: Centers the axle, Corrects left to right pinion, Reduces left to right movement of axle during travel. Lower cost compared to adjustable panhard bar. The axle moves away from the gas tank under full bump and flex.
Disadvantages: Not adjustable, and also doesn't come in different sizes(unless you make your own). the roll center remains at the same height while the center of mass moves up(this makes the truck have more body roll)
Panhard lift(on the axle)
Advantages: Properly centers axle, reduces left to right movement during travel, raises roll center (making the the truck less prone to body roll). The axle moves away from the gas tank under full bump.
Disadvantages: this would have to be made by a shop, unless you can simply weld the drop bracket on the axle? extended bump stops may be required if you match the amount of lift with your suspension lift, you should check for clearance before hand( this being said I have installed a 4.5" lift bracket and my bump stops are extended around 2.5" so you could concievably get away with a 2"-3" lift with no problems. cost is probably still less than the adjustable panhard bar even if you have to have one fabricated and installed. I believe that the axle may move towards the gas tank slightly more than the panhard drop does, but not as much as the adjustable panhard bar.
It is generally accepted that the panhard should be flat if possible because it decreases left to right movement of the axle. I have also heard that a flat panhard bar reduces rear axle steer. additionally if you decrease body roll you have more grip because the load is kept equal on each tire, it also increases side hill stability. on my truck I installed my lift bracket and noticed a huge increase in handling around corners and over bumps, I had to install a new axle in the rear and have not yet installed the lift bracket and have noticed a significant increase in body roll and side to side movement compared to before. more notably without the lift bracket if I floor it going around a corner I can cause one tire to loose traction, when the lift bracket was installed the tires refused to loose traction and just felt much more grippy, I loved the new feeling of the truck so much i went and tested out in the desert immediately. I cant wait to reinstall the lift bracket!
Heres some more information on some of the terms I used
Panhard Bar
Roll Center
Body Roll
4 link with panhard
Hopefully you find this interesting and useful, I spent quite a bit of time researching this, and also a bit of time writing this response.
