Both NUS and NTU are well recognized universities. Your prospect
of landing a job will depend much more on your results than whether
they are from NUS or NTU.
An honours degree will definitely give you better chance in
landing a job (vs no honours). However, a 3-year degree with
straight As will not lose out much, or at all, to a first class
honours degree.
An honours degree will also give you better prospect in getting
into a master degree programme, higher starting pay at government
organization. It is to be obtained at the cost of an additional
year of study (for NUS).
Quality of lecturers wise, it is hard for someone to tell you
unless the person has enrolled in both courses (near impossible).
Given the stringent standards of both universities, I do believe
both have good quality lecturers.
One more thing, an honours degree only counts if it is 2nd upper
and above. A 3rd class honours is, in a way, an embarassment.
You're better off having a bachelor degree instead.
Hope this helps.