For me it comes down to this:
Price, Portability, Power ... (Flexibility and easy of use , as in TTL / HSS)
If you go with Nikon CLS or Canon TTL top of the line Flashes that give you Power/Recycle and Features ... the price difference is not that much "if at all" between a Einstein / AB system with Battery ... and a Four Flash solution , which you would need (at least) in order to have the Power.
But, if you go manual Flashes ... like the New LumoPro LP160 ... just blogged about.
Price advantage goes to Flashes.
But, it needs to be said .. you can cover the Power of four flashes with "just" one strobe. and AB's are cheap. and Einstines are fast and with action stopping power.
Flashes WIN ! period ... more so if you have to fly with them.
But, the AB solution is not bad ... because all you need is one(1) strobe and battery. and again , you have power.
Power: (Power actualy should be the most important)
Strobes WIN ! no question
When you have a need for power ... there is no substitute :)
and you have the option to plug into a wall ... so you can shoot long jobs. with a faster recycle. (and with little overheat worries)
Below shot today Day 7/25/10 : 1/500 HSS, f4, iso200 .. did I have to shoot/flash HSS maybe not ... but I have that option ... so I take it :).
(Flexibility and ease of use , as in TTL / HSS)
A TTL multi Flash system WINS ! ... but, it is also the Most Expensive choice.
Just the triggers alone is $250 each ... and the Flashes at almost $500 for the best one's.
But, you have a TTL solution ... that is a fast event set up. and you have full remote control.
and a HSS solution that allows you to fast shutter in the bright sun (but, you MUST have more flashes and power)
AB strobes with the PX trigger and JrX studio REC allows you to HSS on AB's older strobes with phone jack. But, the Einstein's does NOT have a HSS solution yet.
If you have a Multi TTL flash system, or a Manual flash system ... what you have is Flexibility.
You can take One(1) flash with you (really, really portable) ... or you can take Ten(10) flashes ... you can bring as much gear as the job requires.
The nice thing about multi flashes is you can place them where you need them and control them individually. Of course it also adds a bit of complexity to the set up. But, it also has more possibilities for some dramatic light and creativity. More flashes , more options. :)
Simple might be the best solution ... but, we are talking about what is more Flexible and has more options. (more flashes = more options)
Also need to concider .. a Huge Octibox with grid with a powerful strobe is actually the easiest to use in a studio for a portrait. A bunch of flashes for a portrait will almost always be more difficult. Because of the options and choices that can be made.
Shot today 7/25/10 handheld with flash ... f3.2, 1/50, iso1600 , 86mm
IF, you have time on the set up ... Strobes are the ultimate solution ... more so if you have a Radio Trigger set up (RadioPoppers PX/JrX studio combo) that also allow you to HSS in the sun. AND control the power level of AB stobes via Radio remotely (not Einstiens , yet)
IF, you are an event shooter ... that portability and speed of the "first" shot and set up is more important than Power and Cost. TTL flashes are the ultimate solution.
IF, Cost and Flexibility is the priority , and Power not as much ... a Multi Manual Flash solution is the Best. which is what most Strobist do.
They use Multi Manual Flashes ... Key word is Multi.
For me, the immediate answer was easier ... when I discovered that RadioPopper has not figured out how to HSS on the new Einstein's ... "yet".
HSS is important to me ... because I shoot a ton of f2.8 during the day LOL
That might be out of the norm.
Hope this helps the conversation,
Ross Hamamura http://www.rdhphoto.net/