The x4 23, 24, 25 from what I seen is pretty durable for the most part but I say the t4 line up is stronger. Steering knuckles have been a weak point I seen on the x4 line. I seen arms snap in a bad crash and it's not cheap there. But part support would be better as it's newer. It depends how cheap a 2021 t4 would be and how many spares u can get.