I again recommend a mix of the two. I personally trained at 2 fairly busy airfields, EGKA Shoreham and KFPR Fort Pierce. Definately improved my RT, improved my situational awareness in the circuit etc.
I can also appreciate the benefits of smaller airfields, especially earlier in you training.
Personally I thought Shoreham was a fantastic learning environment, it is busy, has compulsory RT comm with atco, has overhead joins, and a runway you would get nervous landing a microlight on. Shoreham makes the
real pilot in you. It just so happens to have numerous top flight schools there also.
Some people prefer a more gradual learning curve however, and fair enough, learning to fly can be daunting at the best of times!