The price difference between resale and new flat is definitely not so wide. Firstly, new flats are no longer going for 300k..unless it is in areas which are up north like woodlands but still you will pay around 360k. If you look at developed areas like commonwealth, it will cost you at least 500k for a new flat. Resale flat need not be 500k.. it all depends where you want to stay in. 5 room flat ranged from 350k(deep inside Jurong) to 720k (Tiong Bahru).
For new flat, have you factor in renovation cost + interest (if you need to get a loan)? For resale flat, specify to your agent you want to buy a flat that is at least decently renovated. You will save alot becuase you will just need to touch -up (painting, chemical wash, do a few cabinets) rather than the whole house. It is good for young couple as we are low on cash.
If you choose any area near to parents, you will get 40k off the resale price. This is something buyers of new flat are not entitled to unless you are getting DBSS flats.
Lastly, you don't have the pain to ballot and wait for new flat to be constructed if you buy resale.
Hope this will help in your decision making process.