You can't compare the two. The 55-250mm is a telephoto lens that will, at its shortest range, be zoomed in alot into the subject already. the 18-55 can't do much which is why I no longer use it.

Here are some good zoom lenses:

Canon EFS 18-135mm IS ƒ3.5-5.6 (60D kit lens)
Canon EF 28-135mm ƒ3.5-5.6 IS (50D & 7D kit lens)
Canon EF 24-105mm L ƒ4 IS USM (5D mark II lens)
Tamaron EF/EF-S 18-270mm ƒ3.5-6.3

The Tamaron is a near combination of the EF-S 18-55/55-250. It is very expensieve however.
The EF-S 18-135mm offeres the best range out of the canon lenses and is the cheapest of all the canon lenses. It does not have a Ultrasonic motor (USM) and is not weather sealed.

The 28-135mm is closely related to the 24-105 L. They both have a ring type-USM and a focus window. They both allow for full time manual focus (even with the AF switch on). USM allows for much faster autofocus speeds and silences the autofocus motor almost completely. The 28-135mm is not weather sealed.

The 24-105mm Canon L is the most expensive zoom lens available. It costs more than a Canon 60D Body, and more than twice as much a 28-135mm. The "L" stands for Luxury. It produces excellent image quality, and the ƒ stays at 4, from 24 to 105mm. Also, the lens is weather sealed against dust, rain, snow, etc (it is not completely waterproof which means if it's submerged it will break). It features USM and full time manual focus like the 24-105.

I have the 28-135mm and it is a great lens. However, the fact that it is not weather sealed is a big minus. However, it produces good picture quality for a decent price. The 24-105 i have used and is very fun to use (especially if you don't pay for it)