There are many answers to your question. I work with a lot of different photographers and have gone to more workshops than I can count over the last 20 or 30 years. I've seen different lights in use at most of them. There doesn't seem to be one standard.
As for myself, I've used the same set of lights for almost 30 years. I have a Novatron 440ws power pack and 4 heads. I've shot weddings, large events, entertainment news and cover shots for Newspapers and magazines, brochure work, model portfolios and just good old fashion glamour using these lights. When I need a big punch I usually use two heads with one set at 1 stop reduction which means that one head gives 330ws and the other gives 110ws. I've used them in and out of soft boxes. I've always been able to light the scenes I needed to with this setup.
The only problem with the power pack and head based units is that it is sometimes more difficult to setup the lighting ratios except with the more expensive units. Also, no matter what you do with a power pack unit, you essentially never have more ws for all the heads than the pack will provide.
On the other hand if you go with mono-lights of some sort, then each head will have up to its full ws rating, and then can be dialed down from there. Most of the better units will give you a 5 step range. I also like the units that allow the modeling lights to vary with the power reduction so that you can get a "what you see is what you get" preview.
I've made considerable use over the years of White Lightnings and Alien Bees and have found them to work quite well. They are very economical and are American made and supported very well. I've found them to be quite reliable and right on the money for maintaining a constant color temperature.
Being older, and not too good at lifting things, I'd opt now days for something like these Alien Bees simply because they are very compact and fairly light. I also like the fact that you can get a wireless remote controller for a set of lights and then control each light from where ever you're standing. This makes it really east to get just the lighting ratio you want.
I went to a Wedding workshop several years ago where the pro giving the workshop used the White Lightnings ( made by the same people who make Alien Bees - but heavier duty and more expensive) and he was able to do some remarkable things with them using the remote controller.
You'll see lots of information on the Internet either pro or con for the WL and AB's so you might want to research that and read what they say on their websites.
When all is said and done, however, I'd agree with Rolando about getting a light that you can live with for the long haul. Just keep in mind that the price ratios between WLs and ABs and Hensel (for example) can be very large. Also keep in mind the replacement cost of flash tubes, modeling bulbs and the purchase of accessories that will work with the unit. Some models charge an arm and a leg for the replacement items or accessories.
Bottom line: its how you use the lights you have, rather than how much they cost, or what bells and whistles they have.
Here are some shots with various lights. The first is Malloy with a Hensel in a 7 foot softbox:
Here is a shot of Kelley using the Novatron power pack and 4 lights (2 on background and two on model - large 4x3 softbox for main light):
And here is Haley, shot with WL/AB units:
Hope this helps.