Mate I've had no tune, MAF tune, MAF and SD tune, and MAFless... what I've found is it depends on the engine variant, mods, tuner and software as to which is best.
I have an L77, you an LS1, so on the face of it we both have Holden V8s but criteria to inform the best tuning approach is completely different between GenIII LS1 and the latest GenIV L77 engines, specifically due to revisions in ECU speed/capability, MAF resolution, and VE as a result of different ci, heads, cam, intake and exhaust.
On both our engines GM employs two different systems to derive fuel calculations. MAFless (correctly referred to as the Speed Density method) and MAF. SD assumes airflow based on variables like engine RPM, MAP KPA, intake temp, engine volumetric efficiency (VE) values and what not, while the MAF use a sensor that directly measures the amount of air inducted into the engine.
They both have pros and cons, they both have applications when one would be better than other. They both get tuned independently from each other in the GM approach, and combined together at the end to improve part throttle driveability/mpg, etc.
Different manufacturers have their own implementations as well, Ford uses MAF only in all their cars, Chrysler uses SD only. GM had to be wiser as always and they decided to combine both models together.
SD is preferred by most tuners when tuning high performance engines with large camshafts or forced induction. The MAF is removed (or disabled) and the PCM is tuned using the MAP sensor instead. Unfortunately, when the MAF is disconnected the stock PCM has been designed to go into a semi-limp mode (operating from the low octane spark map only).
So that's whereby switching to a completely different, custom PCM operating system from either HPT or EFI will give more flexibility to address specific tuning requirements that, until now, have not been possible.
The new OS restores the high-octane spark map and full adaptive spark control, when operating in SD mode.
On an LS1 this allows the advantage of the latest proven techniques by using software to circumvent the limitations of the LS1's older MAF and slower PCM. In stock form your ECU has trouble implementing fueling transitions as per MAF calcs due to its slower speed, SD uses VE lookups to derive fuel calculations at part throttle conditions. Further tuning the VE will improve driveability, especially on cammed cars, improve l/100k, etc, and would be better suited for FI applications down the track when the stock MAF tune would reach its limit by airflow or frequency.
You can revert to the legacy OS and old MAF tune at any time... oh and don't chuck the MAF away.