Got pro and con. Very much depending on your money and risk appetite. 

New project
- Lower entry cost. Example, can just pay 1k to secure a unit. Rest finance in loan.
- Legal fees borne by developer.
- Need few years to complete while paying progressive interest according to construction stage.
- Unknown end product. All base on artist impression / scale model / marketing brochure etc.

Subsale or Lelong
- Require higher cash in hand. Need 10% downpayment.
- Need own pay legal fees (and stamp duty).
- Completed unit. You can go see, look and feel the property and its surrounding or the view. (But for lelong unit, just able to view from outside, inside condition will be unknown).

Not all bank allow you to finance legal fees (including stamp duty) and valuation fees into the loan.
To be on the safe side, is 10% downpayment and another 5% for legal fees and stamp duty. For subsale/lelong property.

Plus for lelong, case by case basis. Yes will have additional cost that required more cash in hand.