Just as deadly. Also just as deadly as a handgun.
As I've said on here a bunch of times before, the reason gun rights people are so skeptical of gun control people is that gun control people are very specific in that they want ARs banned. Gun rights people know guns, and they know that ARs are no functionally different from traditional-looking hunting rifles.
So that brings up the obvious question, why do you want ARs banned, but not PaPaw's hunting rifle? They do the same thing. Hence the suspicion that once you get ARs banned (the low-hanging fruit), you'll come after rifles generally, and then maybe handguns.
Also mirrors gun control measures in other countries. Give an inch they will take a mile.