(Note for those who receive these posts via email–this article makes reference to a video explanation of this topic that can be viewed here: http://www.youtube.com/watch?v=buFyMnCDctM&feature=youtu.be)
The title of this page, “Speedlights vs. strobes” is somewhat of a misnomer. I use the term “strobes” here as short for “studio strobes,” but in reality, a strobe simply means a flash. The proper name for a strobe in this sense is a “studio strobe” or a monolight. Anyway, now that we have the terminology out of the way, let's get on to the differences.
What is a Speedlight?
A speedlight (sometimes referred to as a “flash gun”) is a portable flash that can be fired on the hotshoe of the camera, or fired wirelessly on a cold shoe. The real advantage of a speedlight is that it can be less expensive, and much more portable. Because speedlights almost always run on AA batteries, they are easy to chuck in your camera bag so they are available whenever needed.
The disadvantage of using speedlights is that they are not as powerful as a studio strobe. A studio strobe can generally pump out at least double the light compared to a speedlight. Also, speedlights have a slow recycle time, which means that you often have to wait between 1.5 and 5 seconds between pops of the flash when the flash is turned up to full power.
What is a studio strobe?
A studio strobe is a larger light that is powered with AC power. You have to either plug it into the wall, or carry a large battery pack (think small car battery) to power it. Studio strobes have lightning fast recycle times, so the photographer never has to wait for the flash to catch up.
Strobes sound great on paper, but they can be quite a bit more hassle to use than a speedlight, because they are not nearly as portable. Also, studio strobes are quite expensive. A quality studio strobe costs between $500 and $1,500. That price increases even more when you consider that lighting modifiers (like umbrellas and softboxes) are more expensive for strobes because they have to include a heavy metal speedring. The price of strobes is increased EVEN MORE when you consider that you'll probably want to purchase a battery pack so that you can use your strobe when no power outlet is available to you.
If you're just learning flash photography and you won't be working in a dedicated studio, I would strongly recommend starting with a simple inexpensive speedlight kit like this one. If you'll be working in a studio, and your favorite passtime is money laundering, then you might enjoy this studio strobe kit at the bottom of the page.
Generally, I use speedlights for shooting wedding receptions, candid photos of my family indoors, as well as 3 or 4 light photo shoots indoors and outdoors when I simply don't want to carry around the bulk of a studio strobe.
I use strobes every time I'm doing photography in the studio, and I often take it to shoot portraits when I'll be outside and competing with a lot of sunlight.