If I go into town and eat in a fast food restaurant, it tends to be Burger King.
My four year old daughter loves the fries served there, and I eat the spicy bean burgers.
It is hard finding acceptable vegetarian food in this kind of fast food outlet, but Burger King produces a filling and tasty snack with the spicy beanburger.
Any vegetarian alternatives in Macdonalds are nowhere near as obvious to the hungry consumer.
As far as cleanliness and staff go, they are more or less the same, although I have noticed that Burger King outlets do not tend to be in such prime sites as Macdonalds, and they seem to be a little shabbier.
Our local Burger King has undergone a refit recently, and looks much better, but is still viewed as the poor relation by many.
I wouldnt drink the coffee or tea in either restaurant, although Mcdonalds does do better coffee.
Prices in either restaurant are the same up and down the UK, although I have noticed each ups their prices at railway stations.
If you are in London the prices probably seem cheap, but in the provinces they seem higher, due to lower wages outside London.
Rather than eating in Burger King or Mcdonalds at all I would recommend eating from a bakers, where you can get a sandwich cheaper, and it will fill you up a lot better.