I have a Pro foto pack system as well as 5 Photogenic Powerlights.
I much prefer my monolights. Each one is self contained, infinitely variable without regard for the other, not tied by distance to the pack, etc.
The Pack systems seem more robust.
Simple example, Set up a monolight 30 fee from a model to the left, and 10 feet to the right...a distance of 40 feet. No big wup. Can't do that with a single pack system, not enough cord lenght.
Put a pack head over a model for a hair light, and then another for the main, you are limited by the cords again, and the ratio.
My Pro Foto pack has 3 outlets. You can plug a "main" into outlet one and 2 heads into the "B" side.
Your only choices of "ratio" are full power, half power, 1/4 power to the main. You can split the B side off and have it fire at full, 1/2 1/4 etc but the 2 lights on the B side are basically tied together. Once you get the basic ratio, then you can turn a knob to vary the output of all by about 2 stops. My monolights by comparison, can adjust in 10th of a stop increments.
I often shoot a rim light, and if you were limited to full, half or quarter power, it severly limits your abilities.
Yeah, you can move the light closer/further to the model, but that changes the effect, wrap around, etc, apart from intensity.
Why then are pack systems so popular? Well, they are built like a brick, and if you are willing to put up with certain limitations, they offer high quality light, longevity, and aren't that hard to deal with once you get the hang of it.
I might be of a different opionion if I could get three or four packs but I can't afford it.
At least with a pack sytem, if you get your ratio right in the first place, a single turn of the knob essentially turns them all up and down in unison, instead of running around and adjusting each one individually.
If a pack goes down, the whole system goes down.
If one of my monolights goes down (never happened yet) I still have 4 others.
I bought my pack sytem generator to run a ring light and got the 2 heads as a package deal.
I rarely use them.
If I was travelling around and shooting a basic 2 light portrait session, then I might use them more often. Or again, if I had 2 packs and multiple light heads, they would be fine.
It's really a matter of choice.
I'm sure the more experience can give you 10 other reasons for using packs.