In terms of a career in law neither university confers greater prestige than the other but Nottingham's law school is notoriously harsh in its marking and degree classifications so you are likely to come out of Bristol with a higher degree mark and even classification. Purely on this basis I would choose Bristol. Having said that, for the Bar anyhow, you are unlikely to work in a Magic Circle firm without a degree from Oxbridge and possible LSE/UCL. I don't know if this is different for solicitors.