OK, but its not a chip, it's a handheld tuner. A chip is a physical EPROM chip that you would install into the PCM with one non stock tune and that would be it, they were popular in the early days of electronic fuel injected vehicles, but the technology has advance beyond them. The handheld tuners have the ability to store up to 10 custom tunes (at least thats what my SCT unit can hold, maybe more on other models) which offers more tune options depending on what you are doing with the vehicle or what fuel is available. Tuners are way more better than the old "chips".
I bought my SCT tuner from 5Star Tuning with 5 custom (to my Ex with all of it's mods taken into consideration when they write the tunes) loaded. I got the 87 Octane Economy, Tow and Performance and 89 Octane Tow and Performance tunes. My EX is a dedicated tow rig for our 11K+ lbs TT, so it sees very few unloaded miles but the Econo tunes does get it into the higher gears at lower speeds and gives good around town put-putting drivability, maybe a slight MPG improvement over stock if this is how your daily drive typically is. I'm a hyper-miler in real life and am always trying to get the best fuel efficiency no matter what I'm driving, even when towing. (I daily drive a '94 Geo metro and it sees 60+ MPG tanks) I found that the Towing tunes were too aggressive to downshift on highway grade climbs to keep the RPMs up, great for the guy that wants to be the first on to the top of the next hill, but not for me. The Performance tunes are a much better match to my personal driving style as they will allow for higher throttle openings under high loads before forcing a downshift out of OD on a climb, more time in OD equals better mileage, so that keeps the fuel miser in me happy. I found through lots of playing around on trips and watching the data that on a "given typical Eastern Interstate Highway decent grade" that at 63/68 MPH the stock tune would force a downshift out of OD at 45% throttle opening, the 87 Perf tune would allow up to 55% throttle opening before dropping down and the 89 Perf tune can go up to 64/65% opening before downshifting. My V-10 with headers, muffler and an effective 4.39 ratio is making enough power/torque to either hold or slowly bleed off a little speed in OD in these situations, if I drop below say 56 on a climb in a 65 zone I will make it drop down and then accelerate back up to speed in 3rd gear then back off and let it shift back up to OD. This is at a combined weight of 19,500+ lbs. For longer or steeper hills I will try to run the approach speed up a little bit to give me a little more room to either make it all in OD or at least more of the climb in OD. I typically get between 8 and 9.5 MPG on our mostly highway towing trips, 7-ish on back country roads with lots of small towns. So that's the real difference for me between the 87 and 89 Octane tunes (I always match my fuel Octane to the tune I'm using) and how I use my EX, not really sure how much better (or worse) the 89 would be over the 87 in unloaded daily driving.
I did recently do a rare unloaded trip from Philly to Columbus and back and decided to play with it on the way home, set the cruise control at 65 MPH the entire way (PSLs from 55 to 70 MPH) and got 14.5 MPG over the 470 mile return trip all on the 89 Octane Perf tune. That's not too bad for a 4" lifted 4X4 V-10 with 35"X12.8" tires and 3 adults onboard.