Well, I thought that I would pitch in here as I worked in a Burger King for several years. It may have changed since I left, but here is what used to be true:
The burgers were frozen 'pattys' and were cooked by passing them through what was called a flame broiler. Essentially a broiler was a metal conveyor that passes through an enclosure with gas tubes below, and what appeared to be electric heating elements above. The flame grilled part comes from the fat within the burger dripping onto the gas flame below it and igniting in a whoosh. This is also why the flame grilled searing marks were only ever on one side of the burger patty

Incidentally the burger pattys were approximately twice the size of the cooked product - you could play Frisbee with them if you wanted! The burgers took approximately 60-70 seconds to go from frozen to fully cooked.
The broiler also toasted the buns by using a separate conveyor. On the other side of the broiler a member of staff would put the burgers into buns and then place them in what was called a steamer. Essentially this was a vat full of steaming water with metal trays suspended over it for placing the burgers on. The heat and steam was kept in via sliding 'doors' on the top. There was a time limit as to how long burgers could be kept in the steamer before being thrown away, but I cant remember how long it was. I think it was supposed to be something like 10 minutes, but normally it was at least half an hour, sometimes an hour. In really slow periods, the food was always cooked fresh as using the steamers generated a lot of needless waste. A good burger prepper would regularly check their steamer and any burger looking less than its best would be binned and the waste recorded.
When an order was placed at the till, it was automatically transferred onto the relevant screen in the kitchen to allow the burger prep guys to make everything needed. There were several screens - one on the whopper counter, one on the cheeseburger counter and one on the chicken and beanburger counter.
The burgers would be made to what was on the screens, but in busy periods certain types of burger would just be made to fill the chutes so customers waited less for their food.
Making a Whopper with cheese (as an example) consisted of firstly marking the burger box with an oil based pencil - you would circle the type of burger, and cross out any ingredients that the customer had asked to be omitted and finally mark the time it was due to be discarded - burgers could only be kept in the chute for 10 mins then they had to be thrown away. The marking was simple and customers in the know could check and ask for a replacement if needed. The marking worked as follows, along the front of the box were the numbers 1-12 and when preparing the burger you checked the time, and if it was 13:20, you would mark the number 6. The till staff would know that when the minute hand of the clock reached 6, the burger had to be thrown away.
Anyway, I digress, to continue making the burger you would then take a burger out of the steamer (at this point it is just the meat in the bread) and remove the crown of the bun. You then placed the meat and the heel of the bun in the burger box and add two slices of processed cheese. You then put the burger and the heel of the bun (still in the box) in the microwave that used a pre set timer to warm the meat and melt the cheese. As this was happening you would spread mayonnaise on the crown of the bun, sprinkle it with lettuce and add two rings of tomato. Once the burger was done in the microwave you would take it out add 4 slices of pickle, some onion and a swirl of ketchup. You would then take the crown of the bun and 'flip' it over onto the burger and close the box and et viola! Off it goes down the chute.
As for the value - BK have always been expensive, but the quality of a good BK burger is far in excess of a MacDonald's. However, I admit it is hit and miss depending on the outlet. Having made many of my own burgers in my time at BK, I can safely say there has never been a MacDonald's burger to match it. I recently had a BK in a newly opened outlet and it was beautiful. It was fresh (I can tell it hadn't seen a steamer for long), hot, well dressed with fresh salad and had a lovely soft fresh bun. One of the best burgers I have had in a long time. Having said that, I'm not sure it was worth the £8+ I paid for the meal and the fries were...well.....meh. Hate em, always have
I was working at BK when they introduced 'king fries' and I have never been a fan. Give me MacDonald's fries any day of the week!
By the way, any good BK will cook your burger to order if you ask them and you don't mind waiting.
I will always prefer a good BK burger over a Macdonald's but I think MacDonlads lead the way because they are so consistent and they are cheaper. They offer a generally cleaner looking and feeling environment too. As with many KFC's, many BK's are often scruffy looking, don't have enough staff and have the kind of toilets you would expect to see in a public park. I think maybe they have invested less into the franchise and don't control it as tightly? However, if you are lucky enough to find a good BK, it is worth a treat every now and then

I hate how expensive BK's are but don't mind paying the price occasionally when I know the outlet is a good one.
I have to say though, MacDonald's is where I often go for my morning cup of coffee, and if I am feeling really naughty I have a chocolate muffin with it!!
Buff