TCX_757,
You should do the subject that interests you the most. You're more likely to enjoy it, you'll be better motivated, and therefore likely to achieve the best grade you can. Then at least you will have kept your options open in an area that you have a liking to.
Suisse Pilatus,
Suggest you read the 1500 odd posts in this thread old bean. You may find the answers you seek, as many before you have. It's a small effort really, if it helps get you more clued up on the selection.
Regards,
Streety.