DW,
your new soreness could just be the result of doing something new/different that your muscles arent used to.
i agree that one of the best ways to train is to keep constant tension. however, you dont have to use light weight and high reps for that. ronnie is a perfect example of that.
personally, i like to combine both. i do 4 sets of 5-15 reps. that way you get both the benefits of the pump and heavy training. i also found that doing the 1st set of 12-15 with a moderate weight, i can actually go heavier with more feeling on my last set when i try to max at 5-6 reps. the higher reps provide a nice cusion. however, if i do all sets of 8-10 reps, i dont feel as deep as a pump or soreness i do if i go extremely heavy on the last set for 6 reps.