Is it better to invest in one 18-135mm lens or have a standard 18-55mm lens and another 55-250mm lens for occasional need?
Things to consider 18-135mm:
- You dont need 135-250mm range.
- You dont like to change lens frequently.
- You want slightly better image quality within consumer grade.
- You want to carry only one lens with you.
Things to consider 18-55mm and 55-250mm:
- You dont mind changing lens often.
- You want the 135-250mm focal range.
- You dont mind the slightly less contrast produced by the 55-250mm.
- You dont mind carrying around multiple lenses with you.
Personally I think, if you want an all in one solution, you should get the 18-200mm, or if you prefer image quality, get the 15-85mm.
There's quite a bit of difference in the focal length range covered by a 18-135mm vs a total range of 18-250mm between two lenses.
Its really a bit of apples and oranges comparison.
If you need the longer focal length, go for the longer setup. If you just need 18-135 range, get that one. Quality wise, they're all consumer zoom lenses and probably about the same.
With my previous (Pentax) camera I have had the 2 kit lens combo (18-55, 55-200) With my latest (Canon) I have the 18-135 and I am not thrilled with this lens. I've done some prior research and was expecting more in terms of image quality. I also didn't think I would miss the extra reach but I do. Thank god I also purchased the prime Canon EF 50mm f/1.4 USM otherwise my Canon experience would have been a sour one. I find the 18-135 so mediocre in terms of image quility, bokeh, etc. (I feels pretty good though) I only use it when I really have to, the prime lens is also the primary lens the moment.
What I should have done was just to get the body (or buy a cheaper older body) and get a pair of decent lenses instead of the one kit. @ShuttterBug has already suggested the 15-85mm which suppose to be very good for its class. Personally I would go with the Canon EF 17-40mm f/4.0 L USM, Canon EF 70-200mm f/4.0 L USM and 50mm f/1.4 USM combo.
However to answer your question; given only those 2 choices I would personally go with the 2 lenses rather then the 18-135.