They are quite similar, they both really hit the posterior chain (erectors, glutes, hams). RDL’s also hit the traps and the grip, which sometimes you want to work but sometimes you don’t. As someone else mentioned the leverage is not the same, the bar is closer to your body in the RDL and a little farther out in the GM which is why the weight is not the same.
Squats and step-ups are the exact same movement, as is a bench press and push-ups, but that doesn’t mean they have the exact same benefits. Use both.