Both have different purpose.
18-55mm will be your everyday lens.
55-250mm will be you occassional lens. Meaning, good for taking pics from a distance. Like football, soccer game, bird photography.
If you can, dont get either of these lenses. Save up on the 18-200mm. You will like this and use this more often.
Ive had those two lenses and i must say that it did the job. But switching lenses was a hassle. You may miss a couple of good shots while doing so.
Another thing to consider, the price of the two lenses is equivalent to the 18-200mm in terms of price.
In the end it will be you who will decide.