I think there are three things really -
reputation - Bath is a top UK university, but as a PP said, UCL is a top university globally
student life - very different vibes, London vs small twee picturesque city - what would they prefer?
year in industry - this could be really good, but I would investigate a bit before making any decisions. Some places advertise this but in reality there aren’t many opportunities and the DC get no help to find them. I would ask what percentage actually find a place each year, if it’s high, happy days.
UCL internships are obviously shorter but the university does help and they might get to experience two different workplaces. Plus if they choose to do a year abroad, some or all of that can be in a workplace too. Internships are probably a bit more flexible too, if they swerve slightly from the career plan.
If they are up for London, I would go for UCL unless Bath tell you that all / nearly all students actually get to do the four years, lots get jobs with their placement companies after etc etc.
But - if they don’t fancy London and would prefer a perhaps less intense campus environment, pick Bath! They’re both great unis, so you can’t lose really.