Many people will argue that grad filters are not necessary these days with digital, and to an extent they are right. You can bracket and merge.
But, there is no doubt that it is much faster to use a grad filter, and also you don’t have to worry about movement between the frames. Even the smallest movement such as that created by the mirror movement can knock the alignment out, which simply results in your merged frames looking out of focus.
But if you are going to buy grad filter, for anything other than hobby use. You have to buy top quality. Or the derogation of you photo will just negate their use.