I have rx and xt on different bikes. both great powerful brakes, but work in a different way.
The xt’s have a very high initial bite feel, will lock the wheel almost instantly making them feel more powerful.
The formula’s have the same amount of stopping power, but deliver it in a more linear way, the more you squeeze the more you get./ Will obviously still lock up either wheel.
Xt’s feel more powerful cos of the almost instant lock up. All comes down to personal preference, i prefer the shimanos over the formula but they require a “better” control of the lever