This question already has an answer here:
I currently have the 35mm Prime, but was thinking of getting the 17-55mm as the f/2.8 is really attractive especially at 17mm for low light photography.
However cost is a concern, and if the image quality cannot compare to the 35mm prime, then I will have to rethink my decision.
I just got my APS-C EOS 70D 6 months ago and I love it so I definitely won't be changing that anytime soon. I'm still an amateur anyway.
Now I spoke to amazon customer service and my 35mm f/2 IS is barely 2 months old and they are willing to refund me the full cost which means I need to top about about 100Euros to get the 17-55mm f/2.8. Now this is definitely very attractive to me.
I also have a Canon 10-18mm which I got recently.
To be fair I like the idea of not having to change my lenses with the 17-55mm while having the f/2.8 at all focal lengths. But it's really costly.
I use my camera 95% for vacations and 5% for pictures of my 1/6 figures and hobby modelling i.e. Macro work.
I just don't know if I will regret giving back the prime and going for the 17-55mm f/2.8 but losing image quality in the process...
P.S. I tend to only buy Canon because I really like the in-camera lens correction profiles. I don't shoot RAW and never post-process my photos.