Depends what you want to watch and do, spot photo etc.
The 'Hall can be slow if no movements, but can have much more intersting visitors. The 'heath can be busier if the F-15s are flying.
The campsite above, also known as John's field is the good for the 'Hall. Costs a pound for the day. With toilet facilities. Where I go if staying for the day at the 'hall. Convienent trailer in the field to photo over the fence.
Lakenheath has a dedicated viewing carpark at the end of the runway. Good for spotting and s-mode but you would have to walk abit if taking photos as you would face the sun if you stayed here.
HTH
Graham
Graham