Although there are some NATS airports where the Approach function is provided at the airfield as opposed to centrally at Swanwick, the provison of approach radar via an area centre will become increasingly the norm.
I am non NATS, but if I was applying for a cadetship now I'd definately go for an aerodrome streaming purely because I enjoy the buzz of working at an airfield and sorting out what goes on on the ground.
That's not to say that area isn't equally as challenging, each discipline has it's own set of challenges and can be equally as daunting.
I would try and decide before the interview what you'd really like to do and don't be afraid to express that desire.