The problem you are running into is one of context. The answer to the problem depends on what's causing the progress to stall. Neither answer is inherently wrong, nor is either answer more correct. For a better answer to your question, I have to introduce the concept of periodization.
At it's simplest definition, periodization is the process of focusing on one aspect of strength for a period of time.
Part of the problem is understanding what is causing you problems at the moment. A good primer is a couple articles by Greg Nuckols:
He does a good job of breaking down otherwise complex topics and making them understandable. Here's some of the pertinent highlights:
- In order to improve strength or size you have to increase the training stress over time
- You may run out of the ability to recover from the training stress
- When that happens you need a new type of training stress to keep progressing
- The mechanism behind achieving these goals is to periodize.
The simplest method of periodization is simply switching between moderate weight/high volume and high weight/moderate volume.
It can get more complicated than that depending on your long term goals, but you have to remove whatever the roadblock is. If you've pretty much stalled progress working with multiple sets of 8-12, you might need some time with reps in the 2-4 range and really push the intensity (weight on the bar) for a few weeks. When you come back to working with the volume, you will invariably be able to use heavier work weights. That helps with increasing the training stress.
In general, I believe that the 8-12 rep range does help with time under tension and the ability to add useful mass. However, you can't live in that and keep progressing just as you can't live in the low rep world and keep progressing. In the first case, you never get accustomed to holding heavy weights which limits how much volume you can practically handle. In the latter case, you never improve your work capacity and can't recover completely in time for your next training session.
You'll find advanced bodybuilders and power lifters train very similarly when you look at the big picture. The main difference is the amount of emphasis size and single rep strength have in the training. My primary emphasis has been strength performance, but I've found that bodybuilding style work has helped me stay healthy, improve my work capacity, and build a more useful frame to use for strength performance. I'm confident the reverse would also be true.