Hiya, I saw your original thread title was "Should I apply for gem at oxford?"
It looks like someone has merged your post into this applicants thread now.
To answer your question - I think you need to split this into two questions - "should I apply for GEM?" and "should I apply to Oxford?". Oxford has pros and cons just like every other uni, if there's a specific worry about it then please share. GEM is a bigger choice and one I'm not sure I am best qualified to help you with.