You are not talking about maxing out, you are talking about training until failure. There are two kinds of failure, positive and negative . I personally think training to positive failure is the best. I combine heavy weights and low reps to train to positive failure most of the time. Positive failure is where you cannot by any means complete 1 more rep without the assistance of a spotter. Negative failure is where you continue do reps even after you are exhausted with the assistance of a spotter. They are helping you complete the rep. This is a heavily debated topic though. Many claim that training to failure causes too much damage to the muscle resulting in a slower recovery time. I personally believe in holding nothing back in the weight room. If I am going to lift I am going to do as much as I can until I cannot do anymore (I usually keep my reps above 5 though). Of course, this style is not for everyone. I suggest trying a couple of different ways to see what is best for you. What is best for me, or someone else will not always work for you.
scott

but how do i know whats best for me? i feel the burn in both of them... i sorda just do it.. till i cant do 1 rep but now that im looking at it.. ill do it till i can do like 3 more or 5 more... and just stop so sorda in between