I always go for good quality beef burgers- get as high percentage of meat as you can (I like beef). I don't buy the ready made burgers like rustler burgers etc. I usually have sainsburys taste the difference aberdeen angus burger steaks (cant recall exact name). They might be higher in PP but I find one is very filling and don't need a second!
I tried the frozen birds eye beef burgers and they are rubbish- during cooking they halve in size and taste really rubbery.