The best part about learning at a dedicated GA airfield (something that Biggin is definitely not) is that you can almost always just power up and go. Somewhere like Biggin you will often need to wait in a queue to line up, and jet/commercial traffic will always get priority over PPL training flights. Then when you're in the circuit you'll get told to orbit to allow something else to join, or be told to go around so that a jet can line up and take off.
Biggin is actually a nice place to fly. You won't generally be waiting in a queue but there will be insanely busy times (usually in the afternoon). Jet traffic does get priority but you won't be told to orbit to "let something else join", most jet traffic will fly straight in on the ILS. You certainly won't ever be told to go around for the benefit of a departing jet. You may find you are told to land and return to the hold for jet arrivals or if there is someone flying circuits in a jet - which isn't very likely - before being able to continue.
The benefits are a HUGE tarmac runway, self-service refuelling (no more bowser chasing!), ATC, and... oh yeah... all that jet traffic (as it will be good experience for you to mix with commercial traffic, in case you actually want to fly somewhere, particularly abroad where English speaking airports tend to be the bigger ones!).
The biggest down side, other than the place being on a hill and therefore a bit closer to the clouds, is the cost of flying there. 10 landings cost over £200! 10 circuits over £70.
You get what you pay for though... did I mention the HUGE runway?
