I found kkamin's post and agreed with it strongly enough to thank him for it. I've written a blog post or two on the "strobist versus big lights" dilemma. As for being able to visualize lighting effects, I think the biggest difference between the "strobist" type of lighting is that when you set the main light, you can visualize the lighting as coming from say high and to the right of the camera, creating a shadow pattern that will create an under-nose shadow that fals at let's call it "between point A and point B". But when aiming let's say a studio flash in a 20 inch parabolic reflector that gives a very similar lighting quality as an umodified speedlight flash, you can actually, literally "SEE" the shadow placement with every single move of the light.
Also, when photographing, with modeling lights, you can actually "SEE" what the light is doing as the subject moves, before the photo is made. With the strobist type of lighting setups, you have to pre-visualize and imagine what the lighting effect is like, and when a subject moves or changes pose significantly, you're back to estimating and previsualizing, whereas with a modeling light fitted studio flash, you can see how the light is falling in relation to the subject all the time.
I liken the strobist process to shoot, chimp, re-adjust light,shoot,chimp, re-adjust light, shoot,chimp, make final adjustment to main light. It's a process that relies on a lot of experience and multiple test shots to get a light placement that could be done in 10 seconds with a modeling light as a real-time, constant guide. Modeling lights will also add up to 250 watts of lighting for each head you bring in, aiding focusing quite a bit by boosting light levels, and also getting peoples' pupils down to normal size.