Hi, I suggest you first decide if you are interested in the Technology sector first as UCL IMB basically already chooses the main modules for you already with only one elective option. This is unlike NUS Biz where you can have the flexibility to choose your own modules. Seeing that you have no career end goal as of yet, I suggest you start thinking about this before deciding as you are limiting yourself in a sector.
As for whether UCL creates a better branding than NUS, I think this is something that everyone will forever be debating about so I don't really see a point in you asking such a general question unless you just want to assure yourself that going with UCL is the right choice.
If you are asking whether UCL creates a better branding/ open more doors in specific sectors (Say prestige sectors like Investment Banking/Consultancy), the answer is yes. However, that does not mean that it is easy to get in (You will be competing with thousands of others through several rounds of interviews). It just means that you have many more opportunities and networking connections in UCL for those sectors compared to NUS. The rationale is because UCL is one of the targeted Unis for those sectors and have employees going down frequently to actively recruit. The market of those sectors is way bigger as compared to Singapore. First years undergraduates of targeted Unis are already getting spring insights to IBDs and MBBs with a fast track to Summer Internships.
So as for you with no general direction (In the sense of sector or goal) as of now, it is kind of impossible to answer whether spending 200,000-250,000SGD is justifiable as compared to studying in NUS.
+1
it impossible to quantify or justify if spending that additional $ is worth it.
You got to ask yourself if that amount of $ dispensable in your family? If it is, then as what @relaxingforfinal have mention, you have to decide what you would like to do in your career as the structure of both degree is quite different. Personally, I would go for UCL, primarily for the experience and the opportunity to work in UK.
If $ does matter (i.e your parents have to take a loan or something), then I don't think UCL or any university in UK (with the exception of OxBridge) will be "worth" the extra >150k SGD, personal opinion again. Regardless of IB or consultancy, a degree from NUS is more than sufficient to get you pass the first stage of application. On a side note, if you really want to work in UK, you could go to NUS, do well, then apply for Masters in the UK again (this time round, you could even enter Oxbridge

). Masters in UK cost between 20-30k GBP and they are mostly 1 year (if you don't do research), so the total cost of that might be around the same as doing a UK bachelor degree.