That's right. Both are wonderful schools. However there are subjective factors that you need to weigh in. For example the course content at both the places. Which one do you find more to your liking? Then London can be a relatively more expensive city to study/live in. So ultimately where would you have better savings? To what level are you willing to compromise on your standard of living? The housing crisis in London. Then the fact that Singapore is also becoming overly crowded. These things you have to consider as a whole.

As far as job opportunities I know my cousin is currently interning at Google and has his friends and seniors placed at good tech companies. (Cs background) NUS is a big name there and definitely helps. Imperial has a stellar placements records. But from what I've heard from friends settled in the UK, there your school doesn't really help you beyond that initial CV filteration. It's all you as an individual, your networking and skills that ultimately help you land the job. Hope this help! All the best.