Tempo's are silly. Counting numbers in your head just wastes mental energy and ruins focus. The only thing you should be focusing on when under the weight, it moving the weight effectively. Explosive concentric, no pause, controlled eccentric.
Anyway I'm not trying to rag on you, just saying:
-tempo's blow for building mass
Are you kidding me? The best gains I've had is from PROPER tempo. The best gains my clients have had is from using proper tempo. (While maintaining great eating habits ofcourse)
Hypertrophy is the total volume of work done at about 80-90% of your MAX. A slow and steady tempo allows you to increase the amount of time your muscles undergo stress... get it?
Good!
KARKY: "Why do you want to go 2 seconds on the concentric instead of just doing it as fast as possible. What are the benifits?"
It depends on your goals. If you go as fast as possible your working muscular endurance. If that's what you want... great. A slower tempo is for hypertrophy and an EVEN slower tempo is for strength gains.
So again, the benefits depend on the outcome you are looking for. They each have their own benefits...