a chip might force you to run a higher octane rating (though they can be flashed with 87 octane tunes, but your power and mileage increases will be smaller and less noticeable.). a programmer will have several different tunes for several different octane ratings...allowing you to run 87 one week, and 98 the next, and get the most out of either.
keep in mind that running higher octane fuel is not always a bad thing. the cost at the pump is higher, but if your engine is tuned to take advantage of the higher octane (a stock vehicle will NOT, thats why running anything higher than 87 in a stock rig is a monumental waste of money), you can actually get considerably better mileage with the higher octane fuel.
my '93 has a distributor, so i can advance the timing without a chip. i started filling up with 98 octane and advanced my timing as far as i could without detonating. i ended up at about 25 degrees base. i did the math at the time (this was over the summer when gas was over $4 a gallon), and in order to break even, my 98 octane fuel only needed to provide something like a 1.5 MPG improvement. i ended up with 2-2.5 MPG improvement, meaning its actually cheaper for me to run high octane fuel.