I should prly start a gym log - yet I don't know how faithful I'll be posting everyday.

I'm on my 3rd week of using the bowflex and LOVING it!
However, everyday I get more familiar with it, the more questions I seem to have.

Here's an example of my workout.
Today is day three of the 7 day circuit.

Bench Press 4 sets of 15 - 90lbs
Chest Fly (incline) 4 sets of 15 - 90lbs
Chest Fly (decline) 4 sets of 15 - 90lbs
Seated Shoulder Press 3 sets of 12 - 80lbs
Crossover Read Delt Row 4 sets of 12 -80lbs
Shoulder Raise 4 sets of 12 - 60lbs
Shoulder Shrug Scapular 4 sets of 15 - 100lbs
Resisted crunch 4 sets of 12 (barely) - 80lbs

This circuit takes me 50 ish minutes.

Not sure what's more important at this time; the plan is to do 2-4 sets of 8-15 reps.
Should I lift heavy and do less sets, or should I get all the sets/reps in even if I'm lifting lighter to do so??