Go for NTU engineering. If u do well, such as getting a 2nd class honours & above, you'll get to make up for the poor results u attained at A levels. NTU is by far an Uni with world class standing and recognised degree certification. Many graduate engineers landed positions in business developments, banking positions (have to start from backend operations though), teaching and civil service. During your time in NTU, u shall continue to interact with high calibre people such as PRC scholars and students from top tier JCs.

If you opt for SIM business, your best shot will possibly be a relationship manager position in banks, sales & customer executive in MNCs (many do recognise SIM degrees), insurance line or local SMEs (for the more unfortunate ones). There will obviously be people who do well in their career but i feel a sizeable number of them will be restrained by the credentials of the degree. We can always argue about the credentials of a SIM degree till the cows come home, as there will surely be advocates & naysayers regarding this matter, but that is not the intent here. Do mind the caveat, that many organisations do not consider SIM graduates. These include government agencies and big 4 accounting firms. There may be exceptions, especially if u have connections, but generally speaking.....no.

By the way, which JC were u from?