Surprised there are still a few of us oldies on here from back in the day.
Firstly, congratulations on your offers!
I had a similar choice to make (around 10 years ago now...) so hopefully I can help. Though keep in mind that I may be a bit biased as I went for Cambridge in the end, and don't know for sure how things might have turned out if I went for UCL or somewhere else.
In short - yes, yes it is. Cambridge (and the other place...) are a league above in terms of prestige. In particular, if you plan to work abroad then everyone has heard of Cambridge whereas the same is not guaranteed of UCL (many people outside of the UK probably couldn't distinguish it from any other London-based uni). If you're into football: Cambridge is in the Champions League while UCL is in the English Premiership.
Cambridge is obviously ideal for academically focussed people, but that is not a prerequisite, and looking at the economists I knew not that many went down the research path. In fact, of the four economists at my college in my year, three of us ended up in investment banking and the other one in law.
There were plenty of people who were the same when I was there. You could spot them in lectures as they would be wearing a suit so they could go off to an interview in the City afterwards.
I agree it is logistically easier to find work experience in the City if you are in London, but as mentioned above plenty of people managed to attend interviews on the same day as lectures (it's under an hour to London on the train). In terms of workload, I can't really compare to UCL but I didn't find it onerous at Cambridge. Just off the top of my head, I found plenty of time to: regularly play for college sports teams (football, badminton, squash), go to formals / bops / go out, participate in college music, watch plays at the ADC, attend debates at the Union, take trips back home, keep up with multiple TV series, etc. And all of this was during the short 8-week terms (so you have over half the year off if you need time to recover anyway
).
Having a degree from Cambridge in Economics would be ideal for any of those careers. As mentioned above, I'm now in 'investment banking' (well, broadly, algorithmic securities trading more specifically).
Obviously it is just my opinion, but I view Cambridge as significantly advantageous compared to UCL for career prospects,
ceteris paribus.
You're welcome!
As you can probably tell by now, I could not recommend it more - Cambridge (and Cambridge Economics) was a thoroughly enjoyable and rewarding experience for me, and I don't think I could have done better going anywhere else.
Happy to discuss further (either on here or via PM) if you have further questions.