First you need to know what's your common used range in your school events/outings
Each have their own plus point.
15-85 is an all purpose lens but not so good in low light... but can be fix by bumping ISO or using flash unit. The 15mm will be good for group shots with tight situation.
17-55...
1) Stylish
2) Comfortable
3) Waterproof
4) Customisable compartment
5) Thick padding to protect your equipments
6) Strong and durable
7) Quick Access to camera
8) Light
9) Different size inserts can be sold separately to fit individual users requirements
I won't ask for cheap but try to be...
I started photography with a 7D and 15-85mm Kit lens.
Believe it or not~ but 15-85mm IQ is comparable to 24-105L only that the build maybe a bit lousier and the fixed f4 aperture.
I tested it myself~ i was once tempted to get L lens 24-105L cause i heard the contrast IQ is better all that, but...
So if i would have switch from a Canon Crop camera with 15-85mm to a FF camera with 24-70mm lens.
The widest side is the same, when i view on both camera??
Is this correct??
What camera you using?
15-85 actually had close to L grade optics~ only the build maybe not as good as L
I owned the 15-85 and was thinking to changed to 24-105L untill i tested out my friend's 24-105L~
I dont find much difference in contrast, wide still 15-85 wider 105L has longer reach but...
In short, you like Canon lenses cause they have more selections of the same model but different grades, specs and prices to suit different needs of their consumers~
Body wise i think both have their good and bad points~
Depends on you or your camera model lor~
Both systems are different~ If you are used to Nikon you might not be used to Canon's system~
Canon lens mostly can be shared among all their DSLR~
Nikon lens had different lens for some different models~ might not be able to bring forward your old lens~...