The data logging is likely the difference as others indicate it allows a much more vehicle-specific tune to be had. In my experience, canned tunes are generally more conservative but can still be as unsafe or even more unsafe than custom tunes which may push the envelope/timing/power/etc more. An example would be my last FI vehicle (whipple-charged Silverado) came with a canned tune with the charger. However, we opted for HPT and discoverd it needed a touch of extra fuel around 4-4500 rpms as it was too close to detonation. With HPT, we were able to add (and reduce) fueling virtually anywhere and everywhere as necessary. A canned tune is likely just gunna run pretty consistent throughout (hopefully ample fuel across all RPMs) but not always as every vehicle is different.