So far, Falcon-9 was the heavy lifter. Now Boeing is coming with claims of more capacity SLS rockets. They are saying that Falcon-9 is too small for deep space exploration. Boeing is now working with NASA to develop much heavier rockets which can be used for deep space programs.
If the claims are true, then the now rocket will be the heaviest ever so far. They say that it has some very unique capabilities which Falcon does not have.
But, strangely, it is not yer clear, why NASA needs such a rocket right now because they have not built anything which can make use of such capabilities which the new rocket has.
Falcon Heavy can lift 64 metric ton weight into the lower-earth orbit.
The new rocket can lift 118 tons.