SPARTAN-Is were regular soldiers given slight biological enhancements to make them superior to other soldiers (srgt Johnson). their children(SPARTAN I.Is) inherited some of the enhancements.
SPARTAN-IIs were taken as children due to their genetic and physcological markers. they were given decades of training, intense biological enhancements, and the powerful MJOLNIR armor. making them strong enough to flip tanks, faster enough to outrun some vehicles, and quick and agile enough to react to almost anything.
SPARTAN-IIIs were children orphaned by the war and trained by a SPARTAN-II. they were given only a handful of years of training before being augmented and given their weaker, but stealthier, SPI armor. they were deployed en masse on suicide missions. the first 2 groups were lost with nearly total casualities on a single highly succesful mission each. the 3rd and final group never got to go on a mission before falling in combat on Onyx.
SPARTAN-IVs were soldiers and given augmentations similiar to the SPARTAN-IIs using SPARTAN-III augmentation procedures. they are given the generation 2 MJOLNIR armor.
where does the average Elite fall on that spectrum? in terms of canon/Heroic as the intended difficulty? I would say they are roughly equivalent to shielded Spartan IIIs.
the lowest ranking elite would probably be matched with ODSTs, the very best with Spartan IIs
Did not read this properly the first time. I need to sleep. Either way, this comparison is a hard one really. Especially since both featured SPARTAN IIs (6 and Chief) have the ultra rare "Hyper Lethal" rating. I would personally just put them all in SPARTAN IV territory given how Noble team was mostly 3s and kicked major Elite butt.