In both these Bradbury stories, technology has run out of control so that humans are no longer running their own lives. The chief difference, however, is while in "There Will Come Soft Rains" technology has wiped out humankind through a nuclear war, in "The Veldt," humanity is still humming along, even if Mr. and Mrs. Hadley have been killed.
"There Will Come Soft Rains" shows the limits of technology: First, too much technology triggers a catastrophic war, but beyond that, the remaining piece of technology, an automatic house, quickly goes awry without humans to control its technological features. Although the house seems human and is treated as a character in the story, its absurdity becomes apparent as it tries to tend to a family that no longer exists. And in the end, nature is stronger than the house, destroying it through fire.
"The Veldt" shows technology running amok: the nursery takes over the parental role in a devastating away, destroying the parents of Peter and Wendy. What was designed to make human life easier turns it into a nightmare. It may be that the nursery will turn on Mr. McClean and the children as it has on the parents, but at the end of the story, we don't know that. Unlike in the first story, the nursery's action seems to be a lone act.