No matter what others may say, my advice is that a longer term
is not necessarily better. This I speak from experience from having
been involved in 2 resale flat transactions. With a longer term,
you'll just end up paying lots more interest to HDB, which I've
heard in some cases - was as much as 1.5x the amount of the
original loan in the end.
Or you can choose a longer term loan initially, but when there's a
lump sum accumulated in your Ordinary account, go and pay the lump
sum to reduce the loan, if possible.