Is imperial that much better than ucl?

If you want to work as a Civil Engineer then you can study at either or even other universities and your job prospects will remain the same because the in Civil jobs looks for experience than degree. Majority of civil engineering jobs are filled by people who took the apprentice route and is still quite popular in this field.
However, if you want to be a Chartered Civil Engineer then you either need a long experience in the field or Masters from a university with 2-3 year experience in the field. Again you can study anywhere as you learn more on the job. That is why Imperial Civil Engineering is not that competitive compared to its other Engineering branches.
The question is if Imperial is better: Even with all this I would say it's good because you learn a lot of transferrable skills so if tomorrow you are not interested in Civil Engineering then you can switch to other jobs easily.
If UCL is comparable: The job prospects are similar, you also get good transferable skills at UCL. Workload might be less but the difference would be marginal. Social life depending on what you are looking for could be better or same. You would find more extroverts at UCL and introverts at Imperial. The social life is accordingly.

Most Engineering jobs would want you to be hands on so experience would be preferable be it any engineering branch.
There are some engineering branches where a good degree from an excellent university would serve you better like nuclear, aerospace, EEE.
Engineering qualification from one is usually similar to another but universities like Imperial, UCL and other top universities also teach you coding, maths heavy content making them better for switching jobs into consultancy, finance etc.

I’m applying for civil engineering and have offers from both. I know imperial is more prestigious and has a better department, but of course it comes with a much higher workload from what I’ve seen. And correct me if I’m wrong, and a significantly worse work/social life balance. I’ve also heard that the quality of teaching is quit bad at ucl, especially in engineering.
Is imperial THAT much better that its worth all this? I mainly care about employment prospects after, and also want to not hate my uni experience.
And if I do undergrad at UCL, then go masters at imperial, is that as good as doing it all at imperial?

I wouldn't take the risk of going ucl then imperial pg, id take the prestigious offer of imperial. But thats me, u may have a really compelling pull to ucl for whatever reason, thats ok

If courses are similar as are if ur home students then prices don't change much, i would reccomend imperial. But again its up to you