Body response?

I noticed that some of my friends respond to different reps and sets. A friend of mine does negatives,swinging weights in a very fast motion but his body seems to grow and he has never changed his training since last year yet it grows. The other does low reps yet he grows,his training is really pathetic,3 sets of 8 reps,he trains using weights that arent so heavy yet he grows. My training partner does 20 reps for biceps,pyramiding the weights with each set,lat pulldowns 10 sets of 20 reps,his body doesnt really show any origress when he used low reps and heavy weights with proper form,doesn't feel the pump he said like when he used high reps and a pyramided set. So does different body respond differently? How often should we change our training style? Am i training wrongly? My body cannot get a pump when using hEAvy weight low reps. I only see progress when i do lots and lots of reps,i get more then 8 hours of sleep and i eat alot.