Originally posted by ismaelg ... you already have the 18-55, and it seems the 18-250 is not going to be a major difference in performance in that range, ...
Actually, the 18-250 performs better than the 18-55 from about 35mm on up, and is noticeably faster (f/4.5) at 50-55mm than is the 18-55 (f/5.6).
There is another consideration for the 18-250 vs an 18-55 + 55-300 pair: lens swapping. I and others find that we do much shooting in the 28-80mm range. Swapping lenses at 55mm is more than just inconvenient -- it breaks up that flow. I've tried an 18-55 + manual 60-300 pair and I just don't use it for that very reason. I'll more likely use a 35-70 or 28-80.
The 18-55 and 55-300 are both fine lenses WITHIN THEIR ZONES. The 18-250 just has a more usable zone, especially for street shooting.
Look at it this way: Each lens has its own "window on the world". When we use that lens, we see through its window; we see what can be shot with it, and we tend to bypass what can't. We tend to see closer wider scenes with the 18-55 and further narrower scenes with the 55-300 and its ilk. If I *know* I want a longer reach, a longer view, I use a 100-300 or 170-500 -- and I skip the closer wider shots because I know they're unreachable. Similarly with a 10-17 FE or 10-24 UW -- narrower scenes are just unavailable. Their windows only open just so much and no more.
So the 18-55 lets me see in the 'scapes-to-portraits range, and a 55-300 lets me see in the portraits-to-peaks range -- and the 18-250 gives me ALL of those.