As far as i understand, below are the differences between OPS and UPS
1. OPS is 50% of last drawn pay. Last drawn pay for OPS include basic pay, DA, different allowances etc. UPS is based 50% of basic pay. Point to note here is, DA get reset/merged with basic pay on Pay revision.
2. When employee joined service under OPS, they used to pay 10% of salary to his/her PF (GPF) account. Employee who joined service with NPS, they used to give 10% of salary to NPS, employer also contribute to NPS (not PF). All PF amount incase of OPS or maximum of 60% of NPS corpus is given back to emplyee on retirement as lumpsum. In UPS, 10% deduction will happen, but it will not go to any PF or NPS, but it will go to UPS fund. Employee on retirement will not get PF type of payment for their 10% deduction. But there are other new type of lumpsum amount for retirement: 1/10th of monthly emoluments (pay + DA) as on the date of superannuation for every completed six months. i.e. if person is retiring after 30 year of job they will get 6 month salary ( pay + DA) as the new emolument. Gratuity will be same for both scheme.
3. DA is applicable for OPS, but not for UPS. for UPS, inflation index is used. Both can be treated equal.
4. For OPS, base pay for pension changes with each pay commission. For UPS, it is not clear how base pay for pension will be updated with pay commission implementation.
Above information is only for rough information which may not be fully accurate, it will be updated after information will get more clear.