Canon 17-55mm or sigma 18-35mm ?

I think I'm beginning to get it now.

1) Single lens option:

a) Entry level stock EF-S 18-55 STM

b) Wide range zoom EF-S 15-85

c) Wide range long zoom EF-S 18-135 STM

d) There is a very wide range long zoom EF-S 18-200, but it may be a bit old.

Understand that the single lens option will:

a) never be that ultra wide,

b) never be that long,

c) may not be huge in aperture.

2) Multi lens option:

a) Something like an EF-S 10-22 ultra wide

b) Something like an EF-S 55-250 tele, or beyond etc.

c) Wide aperture options:

i) Traditionally, the EF-S 17-55 f/2.8 was a zoom lens that bridged the gap to wide aperture prime lenses.

ii) Now enter the Sigma 18-35 f/1.8; it is only wide-normal for focal length, and not long, but it packs a bigger aperture.

Thus both the EF-S 17-55 f2.8 and the Sigma 18-35 f1.8 are good, but in different ways; both have their strengths and weaknesses.

For a combination of zoom range and aperture compromise, still go for EF-S 17-55 f2.8.

For outright aperture, but a narrower zoom range, and for something that is even closer to a single focal length prime lens, go for the Sigma 18-35 f1.8.

3) Truly wide apertures and prime lenses.

For a truly wide aperture, we must go to single focal length prime lenses.

However there aren't too many prime lenses dedicated to crop sensors.

4) For a truly wide range of lenses in general, and wide aperture prime lenses, we must move to full frame sensors...