Go and visit both, see which feels 'right' to you, examine the course, consider if you want to live in Guildford or Brighton... you need to look beyond the league tables to get the best result for you.
For academics it depends on the subject, like for Engineering and Physics, Surrey definitely has the upper hand. However the city of Brighton sounds like a pretty great place to live as a student, whereas Guildford is pretty limited without trips to London.
For academics it depends on the subject, like for Engineering and Physics, Surrey definitely has the upper hand.
Very debatable, Sussex is one of the only unis in the UK with so many of its physics lecturers working at Cern or are involved with the Cern project in Switzerland (pretty reputable physics department although Manchester's is probably better by a little bit).
As for engineering the "best mechanical engineering student in Europe" in the 2013 awards was from Sussex uni (bear in mind students from Imperial, Southampton, Bristol all send in applicants for this award and Sussex came on top...)
It may not have as big of a reputation as Surrey overall but it is definitely up there in top 30 easily when it comes to academics they can compete with the very best.