My local butchers, Scotts, in Ormskirk, sell a couple of different burgers including pork and apple, traditional beef and "healthy" turkey burgers. I was curious as to just how healthy they were and so Googled "turkey burger calories" and "beef burger calories" - turns out the former has 300 calories less. Obviously, this will vary from brand to brand and butcher to butcher, depending on fat ratios and other ingredients, etc.
Now for processed cheese. I'm expecting to be shot down for this, but on my burgers I like to have processed cheese slices. Don't get me wrong, if I'm in the mood I quite like to have blue cheese or gouda, etc. but I'd be just as happy with cheese slices. I love they way they melt under the grill, forming a lumpy terrain that follows the burger. I love the stringy-ness as I take a bite. I suppose I love way they are just the right size to sit nicely on to the average burger.
So, whether you're looking for a healthy burger or something not as heavy as a beef burger or just looking to save the pennies (90p/burger), turkey burgers aren't a bad choice at all.