Your square tube is probably stronger than a 16ga round - wall thickness can always make up for the inherent weakness of square.
The real tradeoff is how far to go - the roof has a max capacity of 300# total, especially along the nutsert line as the factory designed it. As good evidence on mine, these will pull out with a heavy load or too much racheting on a tie down. So the total weight of the rack must be subtracted to get the actual amount of load you can carry. Plus getting the thing up there, to boot.
Gutter mounts are much stronger for carrying loads and, depending on the style of carrier, have exceeded 500# loads. Ok for travel, not so good for offroad, where more load on the roof equals more incentive to tip over. It's the major problem with any roof rack - along with a loss in gas mileage hauling it around. So the thing comes off when you get to the wheeling site, and in between.
Having lived with a 3/4 rack on my Dad's '60 VW Bus, and then using a car top carrier on a '78 Zephyr, then a '90 Caravan, I don't see the point compared to a nice 5x8 ft trailer. I think the infatuation with racks comes from the Land Rover side of 4 wheeling - one simply can't travel to Africa with a lot of stuff ( and the climate does cooperate in that.) So racks are a fair solution for a vehicle with 4 passengers and limited interior space - and they do ok for Cherokees.
With the trailer - which is what Gojeep uses in Australia - you can haul a more bulky load, more safely off road, and even use the trailer bed for the tent floor. I've even seen a tent camper built this way - the upper cargo floor flipped over, erecting the tent like a pop up picture book. And having spent some time in the military, putting up shelter fast is a big plus, whether a tent, pop up trailer, or otherwise.
I took the rack off my Cherokee - just another way to approach the same solution, how to haul a bunch of stuff. The trailer has carried a pallet of 4" partition block. A roof rack? Well, it has it's limitations.
