There is a difference between programmers, and chips. The chips plug into the pcm. Powertrain Control Module. With 6 adjustable custom tunes that are built by the tuner and mapped out specifically for your truck. PCM code, year, trans, mods, ect. Programmers, such as the Hypertech, Edge, Diablosport, or Bully Dog, plug into the OBD port and flash the pcm with ONE tune. There are several problems with this. One is you can only run that one tune. To switch means you would have to go thru the whole tuning process again. Two, is these programmers can 'lock' to the truck and not be able to be returned to stock, and they can also leave a footprint. Three, you have less tuning capabilities thru the OBD then you do plugged straight into the PCM. The custom tuners for the 6 position chips are able to do ALOT more, tuning wise, thru the chips then Edge or Hypertech can do with thier little programmers.
Also, with a chip, you can tune for things like bigger injectors, bigger HPOP's, and other things. Matter of fact, for you to get the most out of bigger injectors and bigger hpops, you HAVE to run chip custom tuning.