For all practical purposes, any of the EF-S 18-55mm f/3.5-5.6 IS/IS II/IS STM lenses are totally redundant if you already have an EF-S 17-85mm f/4-5.6 IS in good working condition.
What you should not do is buy another lens because it is very marginally better on paper than your current lens. That's how you waste money on GAS (Gear Acquisition Syndrome).
There may be a few edge cases where the extra 1/3 stop of aperture below 32mm and the extra rated one stop of IS may help, but those will be fairly limited to shots that will look barely better with one than the other in very specific scenarios (handheld photos of static scenes in low light). Good technique can go a lot further than 1/3 stop of aperture or even one stop of IS does. If you're using a tripod, as you should for static scenes in low light, or if your subject or other parts of the scene are in motion, then there's no real difference between the two lenses.
Well, unless you want to take a shot at focal lengths between 55-85mm. Which one outperforms the other there should be fairly obvious.
If you really want to replace or supplement the 17-85mm lens with another lens that opens up possibilities the 17-85mm lens doesn't allow, you should think more in terms of true qualitative improvements such as:
- Faster aperture zooms, like a 17-50/55mm constant aperture f/2.8 lens
- Wider focal lengths, like a 10-22mm or 10-18mm
- Longer focal lengths, like a 55-250mm or 70-300mm zoom
- Very wide aperture prime lenses, like a 50mm f/1.8, 50mm f/1.4, 35mm f/2, 85mm f/1.8, etc. which also tend to be sharper than zoom lenses when stopped down to the common apertures they share with those zoom lenses.
But don't go buying such lenses just because someone else, like me, tells you to. Buy whichever one you need when you realize which one will let you do something you want to do with your camera that your current lens does not allow.
The copy-to-copy variation from one copy of the 17-85mm to another copy of the 17-82mm, and from one copy of an 18-55mm STM to another copy of an 18-55mm STM can be larger than the measured differences between the 17-85mm and 18-55mm STM shown at sites like DxO Mark. So you might wind up with an 18-55mm STM lens that looks better at DxO, but the copy of the 18-55mm you actually get isn't as good as the copy of the 17-85mm lens you already have!
This can be particularly the case when buying lower priced lenses used. Lots of folks will buy/return/sell lower cost lenses until they find a "good" one, which often actually means it matches up to their particular camera body and its variations within manufacturing tolerances better than another copy of the same lens does. But sometimes it means cheaper lenses that are slightly out of alignment show up more often on the used market than more pristine copies. Even with very expensive lenses, finding someone who can do an expert job of lining up a lens is difficult. With cheap lenses, it often would cost more in labor to properly adjust the alignment than the lens is worth, and that's assuming the lens even has provisions for optical adjustments. Some lower cost designs do not. So folks will buy/sell multiple copies until they get one they want to keep.
As we said in our answer to your original question to which this one is a follow-up:
Lens decisions are an intensely personal thing. What one photographer may consider essential can be totally superfluous for another photographer. The more you know about how you want to shoot, the better informed you'll be to decide which lenses are best for you when the time comes to start spending more on gear. What one must be careful to avoid with this strategy is the constant desire to frequently upgrade to a slightly better lens (or camera) than what one is currently using.
and (slightly paraphrased):
At this point you don't even know how much you'll enjoy (or not enjoy) photography as a hobby. Assuming you do decide to stay in it for a while, you might surprise yourself with what kinds of things you find you enjoy shooting the most and what type of things you quickly grow tired of shooting. It would be a shame to find any lenses you wasted money on near the beginning of your photographic journey aren't well suited to what you eventually find you most want to shoot.
In all likelihood, if you decide to stick with photography as a serious hobby, you're going to outgrow either one of these lenses relatively early in your photographic development. Don't waste money buying a redundant lens that is, for all practical purposes, no better and less useful than the one you already have!
In other words, start out at the ground floor and wait there until you know enough to know where in the building you want to end up, then use the elevator to go directly there instead of climbing the stairs one floor at a time using all of your energy (money) wandering around looking for where you want to go.