I used to work in Burger King (and Pizza Hut) and do like the flame grilled burgers but really not keen on the fries with the coating stuff they have on them. I like that you can get more salad in them though.
Overall though I prefer Maccy D's, cheaper and I love the fries in there and there is more variety of things I'd choose off the menu.
I have to say though, in town the Maccy D's are much nicer than the Burger King which always seems to be full of quite dense, slow and often rude staff who seem to have little idea about customer service or common sense, another reason I don't tend to go in. In one local Maccy D's I went to recently I counted over 20 members of staff just behind the counter at one time at a busy period and they still managed a speedy, efficient and perfectly friendly service.
Maybe it was also the free staff meals - overkill!