This is not an anti LGW and pro STN post, So please dont bite me !
I find LGW security staff to be very rude I have flown out of the south terminal 7 times in 2011 and not once were the security staff friendly, No reply to good morning, staff very rude to people who dont travel much and dont play by the rules of security.
On the other hand, I have flown out of STN over 10 times in 2011 and not once had any problem with the security staff they reply to good morning they are friendly and the security area is always maned to cope with the foot fall even in peak times.