You get triple the engagement points (if not more, Chris king is almost 7x the engagement points and true precision is 10x the engagment points) which is the most obvious advantage. I am not sure about weight but some of the more expensive ones are lighter (hadley isn't as it is for dh). They also tend to be more durable under the bigger strains of dh and freeriding.

XT's are easy to get, cheap to replace and fairly durable.