The courses you're referring to are General Engineering courses. At least at Cambridge, I believe you spend the first two years doing common subjects which are relevant to most areas of engineering (maths, thermo, control, management) before specialising in your preferred area for the last two years. I don't know what gets printed on the certificate - whether it's just 'engineering' or the specialisation you chose. As for more valued, it probably depends on the job. By it's nature it's less specialised so your depth of knowledge may be less in some areas than someone who studied a specific course, but the Oxford/Cambridge tag has it's own prestige. Jobs such as naval architecture may prefer someone who has spent their whole degree on that as it's a relatively specialised subject, but a bank looking for numerate, intelligent people probably isn't interested in the branch of engineering you studied.