your unit is low floor or high floor?
the payment schedule would be:
1st 10% upon signing SPA
2nd 10% upon completion of work below ground level of the building
3rd 15% upon completion of your parcel
if your unit is high level, and taking non-DIBS, you need to pay the interest of 5% of your purchase price from the completion of the ground level until the completion of your parcel, so is very worth to take non-DIBS
if it is low level, means the period in between paying 5% interest and 20% (15 +5) interests is short.
But anyhow, the rebate is 7% instead of others developers only offer 3% to compensate the abolishment of DIBS, also the payment schedule is charge upon COMPLETION but not COMMENCEMENT, so i think go for 7% discount should be better...