Opticallimits

Not that it will be my primary lens. 

just a backup in case of failure of the great 17-55f2.8 or in case I have to use two APS-C bodies at the same time 

range etc in of no importance, just the image quality and reliability as well as autofocus perfomance  are important 

Which one would be your recommendation?

 

Either one will do fine. Choose according to what you prefer focal range wise.

Quote:Either one will do fine. Choose according to what you prefer focal range wise.

I just need them in the 18-55 range, you mean image quality and AF performance are barely noticeable between those two ?

Are they equally reliable