which would build more mass?

3 x 8 flat bench or 8 x 3 flat bench at more weight?

thanks

do 5 X 3, at like 75, 80, 85, 90, and 95% of your max for 3-5 reps

8X3 would build more mass. Or you could work up to a heavy double or triple over 8 sets. You might even try the 8X3 for one main movement and follow it up with a 3X8 as an assitance movement.

How long would you rest between sets? at just 3 reps per set. and what do you mean by one main movement and assitance movement. thanks for the help guys.

120 seconds would be the max that you'd need to rest. Let's say you're having a chest day, you'd have one main movment (bench) and one assistance movement-incline db flyes.

I'm actually kinda terming that wrong, the assistance movements would be more like tricep work because it assists in the chest movements.