If the IS is decent, it might more than make up for the difference.
I'm sure the IS will be decent (4 stops at least). But it doesn't make up for the 1-stop difference if your subjects are moving. Fine - a 16/17mm lens with 4-stop IS can be handheld down to 1 second (4 stops slower than 1/focal length). But that's not going to help if your subject is moving. Only a wider aperture (or flash) will do that. Granted, one stop is not a lot - but it's the difference between 1/30 s (where involuntary motion in a posing subject can still cause a little blur) and 1/60 s (which will freeze that involuntary motion).
But isn't 4 stops IS better than one stop natural light? Going from an F4 with no IS to an F4 with modern, 4-stop IS makes it better than an older 2.8, right?
As Awinphoto stated, on short(ish) lenses, IS only helps with static subjects (on long lenses, even shutter speeds fast enough to stop many subjects are not enough to stop camera shake, and IS also helps with a stable viewfinder).
The point is that IS allows you to shoot at a slower shutter speed than otherwise possible based on how steady you can hold the camera. The only kind of motion it counteracts is camera motion, IS does nothing to help subject
motion - in fact, it can make subject motion worse (as in my example above - a moving subject will be a lot blurier with a 1 second exposure than with a 1/15 s exposure). If you need a faster shutter speed to stop subject motion, you need a wider aperture, or a higher ISO.