Exeter is a lot more prestigious, and with your grades, you will definitely get in, but it depends on whether they have any places left for psychology, which they probably will, but there is no guarantee. However, if you really don't want to go to City, go for Extra because at the end of the day, you have to spend at least 3 years there.
Exeter is a nice campus uni, and the city is nice; however, the rumours about the nightlife being worse than other places are true to a degree. All in all, go for where you will be happier because you do have to live there, but Exeter is by far more prestigious, so do take that into account too!
Good luck with your A-levels