In halacha is in the same badness to kiss a girl as it is to touch her? Due to the fact that they both lead to the ultimate badness of a זנות?
From a halachic standpoint, both are equally bad in the sense that both touching and kissing are biblically prohibited. There is a certain aspect, by which kissing might be worse, and that is because the way that heaven punishes for sinning is dependent to a degree on the amount of enjoyment that the person had while committing the sin. The more enjoyment the person had while committing the sin, the more severe the punishment is. In that sense, if the person had more enjoyment from one vs. the other, although both are equally forbidden, the punishment for one would be worse.
Rambam Hilchos Isurei Biah 21-1.