both groups of soldiers have weaknesses and strengths and pro's and con's. the spartan is physically stronger and has better reaction times ect. but the genetic augmentations are extremly expensive and very risky. out of all the selected candidates only a few made it to active duty. whereas odst are in greater number and are cheaper to train and upkeep. the spartan mjolnir armour costs as much as a unsc destroyer enough to train over a hundred odst maybe even thousands. spartean 2s are also near impossible to replace whereas odst are expendable. however spartans have a legendary stature and are more well known and looked up to more by civillians (only spartan 2s though spartan 3 project never became public).better 4 morale.i think it takes more skill to be an odst as these guys have been in the -blam!- as marines and worked their way up to the elite. spartans have been made the way they are by augmentations and have had a bigger headstart over the odst. it takes alot less skill to be a spartan. the spartan 2 project as well as 3 are severly unethical as well. in the spartan 2 project the candidates are kidnapped at the age of 5 or six and indoctrinated into a world of harshness and hatred. the augmentation also has a low success rate. many kids were left deformed or died in the progress. the spartan 3 project was unethical as spartan 3s were sent on suicide missions with exeption of noble and the headhunters who were assigned to black ops missions. all but 2 of the beta company spartans died when trying to destroy covenant capabilities on pegasi delta. although success rates were higher and survival rates alot better. odst are also not far off spartan 3s. spartan 3s are alot weaker than spartan 2s closer to odst. the spi armour is not alot better than the odst armour. tbh it is hard to say which one is better