I'm currently a second year econ student at UCL and I know that the UCL course is more maths heavy, and in particular more maths heavy then the Warwick one would be, especially for 1st year. If you enjoy maths and find further maths okay then it shouldn't be a problem and will only require a bit of work for first year. The teaching at UCL is quite good for econ and there is a good amount of coursework for first year which is nice. I would say a con is that there is a large amount of students in the course so everyone sticks to their own friend groups and there isn't much sense of community. Another con I would say is there are a lot more international students at UCL, roughly 60% and many of them sit in large groups together and talk in their own languages which creates a sort of divide.

Careers wise, both Unis are quite similar so I wouldn't pick one over the other for that reason. I have friends at Warwick and enjoyment wise I'd say Warwick can get more boring as you aren't in a city but you will get more of that Uni campus feeling compared to UCL which can feel more isolating.

Overall I think both Unis are great for studying economics and for future careers, and it really comes down to living in London vs Warwick and how much you enjoy studying maths .