Retirement is much better. Tricare, alone, is probably worth $12,000 a year depending on the your current and future injuries. Not sure how much you care about having access to on-base activities, but the Exchange and Commisary are still good deals. There are also the MWR stuff available...
None of the above is available to a separated Service Member. It isn't all about the money, but a severance usually sucks financially. If you are separated, unless combat-related, you pay-back the severance in your VA checks. (Usually, no VA check until you pay the severance back) So for most, severance is just an advance of VA pay.