The 320 and 270 both feature FP for high speed synch. The limiting factor here would be their power output. HSS cuts the effective distance of your flash quite significantly so these weaker flashes would only be good for HSS at much shorter distances than the 580 or 430. If you are trying to use HSS to shoot sports more than a few feet away it is not going to work well for you, especially with the less powerful flashes.

None of Canon's current flashes have built-in optical slave triggers. This is because Canon's A-TTL, E-TTL, and E-TTL II systems rely on weak (about 30% power) pre-flashe for calculating the flash metering. Additionally, Canon's IR and built-in wireless triggers (on the T3i, 60D and 7D) use pre-flash pulses to communicate to send instructions to slave flashes. These pre-flash bursts trigger would trigger optical slaves to fire before the camera's shutter is open, so they are unusable with Canon's modern cameras*.

All of that said, let me add my concurrence to what bob williams and neuroanatomist wrote: start with a good Canon Speedlite before you branch out into 3rd party brands or specialty flashes. I've never known anyone to have been unhappy with a 430EX II, even if it didn't have as much power as they ultimately felt they needed. It has excellent power (for not being the top of the line offering), tilts and swivels, is well constructed (though not as bomb proof as the 580), and is 100% compatible with all of your camera's automated systems. If you have money to spare, then by all means get the 580. If you are just shooting around the house and have no creative ambitions, then maybe the 320 or 270 would be okay for you. Otherwise, I'd advise anyone in your position to get the 430.



(*This statement is mostly true. )