I was in the same situation a while back so I bought both and BF4 is without doubt a lot better. Ghosts does't look in the same league as BF4 graphics wise and that's with both set to ultra. I have some issues still with both games as they crash on the odd occasion but Ghosts may be working for some in multi GPU setups but just google the amount of people that cannot get it to run properly, and I'm one of them. Out of the 30 odd games I have, Ghosts is by far the worst for my crossfire setup and that is including games over 5 years old!
I have been in contact with Infinity Ward and Activision on twitter but still no joy, any updates or 'fixes' they have done is purely for gametypes/addons and certainly not to help the guys who paid full price!