hi,im trying to choose between the Canon Speedlite 430EX and the Sigma EF-500 DG Super for the canon EOS 400D,wich one is better ????? knowing that the sigma is more powerfull/full featured than the Canon one,but will it work in harmony (ETTL ....) with the 400D ????

Does anyone tried it / test it before ???? i need an answer on that cause im about to choose between one of the two.

I would recommend that you try the flash on your camera before you purchase it.
Can't say for the 400D but purchased a ProMaster flash for my Canon 20D. The ProMaster would not work. Not because there was anything wrong with the Flash. But found out that on my 20D and any third party Flashes with a metal foot won't work. Third Party flashes with plastic feet will.
Contacted Canon and they bluntly told me it was a third party flash and it was their fault for the way they engineered the flash.
Have found out that, that the last two pins on the flash didn't make contact with the shoe. Put a paper wedge between the flash foot and the camera shoe and it worked perfectly.
But didn't want to mess every time of putting this wedge in.Since, I did buy the flash locally, they took it back and I got the 430 flash.

Newbie here
rovowen

I have a 400D and both of the flashes you list. Both work fine on a 400D.

Price wise the Sigma wins but build and ease of use make the Canon my favorite. The Sigma feels (and is) flimsy in your hands but it does get the job done. Just be careful with the door to the battery compartment, as it will come off and is the very devil to get back on!!

The Canon recycles faster too.