An IRS can provide extremely good traction, as it is has the ability to keep the tires planted more evenly as the body tries to rotate on launch. The issues with it are typically cost, breakage, weight, and slightly more rotational loss.
The EB is actually loaded properly, not like that Shelby. I remember that ordeal, but the EB looks a lot more organic, theres actually wrinkle and load on the rear tires lol.