I play it on the xbox360, it is WORTH buying even if its 70$ instead of 60 for the xbox360, BEST game I've EVER played on a xbox360.
I also played it on casual and made all bad decision so my renegade would be max lol.
After you beat the game, theres two options.(If u think this is spoiler just dont read, it doesn't relate to the story)
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After you beat the game, theres two options.
*Continue with your character and finish all unfinished missions.
*Continue your character in a new game with all your stats etc saved and bonus credits.
EVERYthing you do in the game changes the ending!!
EDIT:
Btw if you have questions or want tips like how to build relationship(SMEXing with Miranda etc)
Check this link, you can ask whatever questions. I can answer them quick!