Hi, if you're considering either the 17-40/4 or the 17-55/2.8 as a replacement for the standard zoom, nearly all answers in this forum will point to the EF-S 17-55. It is better on almost every single point compared to the 17-40, the exceptions I can think of is weather sealing and FF-compatibility. If you for some reason would need either sealing or FF-compatibility in the future, I recommend you to re-consider then. For the moment I would definitely say you should go for the EF-S 17-55 f/2.8.

(Of course there are other lenses, but if you choose between those two the 17-55 is the best option.)

Good luck!