On a ridgid a fat front tire will help reduce some of the impacts to your hands and wrists and improve traction to your steering wheel. The rear wheel is more heavily weighted so a narrower high pressure tire on the rear will have more effect on the rolling resistance.
For the same size wheel the difference in tire size is usually too small to be noticable in changing the geometry of the bike, so I wouldn't be concerned.
For off-road a fat knobbie front tire with a slicker rear tire can be effective in dry conditions but for road commuting stick to slicks. Knobbies will only slow you down for no good.
A nice commuting combination might be a Big Apple front (2.0" or 2.35") with a 1.5" slick for the rear (Marathon Slick?). Also consider you are more likely to get a flat on a rear tire so I would spend more for flat protection for the rear tire than the front which maybe OK with a cheap tire.
I usually run the same tire or nearly the same as I try to fit as large as possible tire on my road bikes. For MTBs you have much more flexibility in tire width.
Craig