Does the Sigma 18-250mm f/3.5-6.3 beat these two lenses?

[TheBiles]

I've got the kit lens, EF-S 18-55mm f/3.5-5.6 IS II, and a cheapo telephoto zoom, EF-S 55-250mm f/4-5.6 I, and I was wondering if the Sigma provided better image quality. I know it's not the best lens ever, but I really would like a walkaround lens, and these two are a pain in the ass to switch between. I also figure I may be able to find a 2-for-1 trade with these two since they're in the same "ballpark." Thoughts?

 

[zamanakhan]

i dont know about canon but compared to nikon 18-55 and 55-200 nikon versions are actually alot sharper than even the nikon 18-200 so sigma doesnt stand a chance, Its just the convenience of having such a large zoom range. I've been thinking of getting the sigma too but not really too sure, i had an 18-55 and a 55-200 but sold them kinda regret it now.