I've never owned an external flash and am considering purchasing either a canon 430ex II or a Yongnuo YN-560 II. I like the price of the YN560 because it leaves cash to help pay for the prime lens I want, but I'm not sure how important the E-TTL compatibility is on the canon. Is it worth the extra $125?
will your shot stay the same across a number of trial & error shots? if so, seems to me you can be quite happy w/o TTL. if not, then I would spring for a TTL flash.
you can get a 270EX or 270EXII for ~$100, btw, it has TTL. people may think that's not enough power, but it's plenty for many/most situations. (no focus assist light, that's a bummer. and you can't bounce easily when shooting portrait orientation... but I digress)
Unless you still own an older film EOS camera, having TTL is not necessary. Why? All EOS DSLR use E-TTL (pre-flash metering) since TTL works by metering light reflected off the film emulsion at the moment of exposure and, obviously, TLL won't work with CMOS sensors. If you have a late model film camera like an EOS 3, 1V or Elan 7 series they are compatible with both TTL and E-TTL so an E-TTL only flash should be fine.
One issue I've noticed with aftermarket flash units, even dedicated ones, is the AF assist doesn't work with the outer AF points. Something else to consider.
If you are using the flash on camera, then you want e-ttl. I use 4-5 Yongnuo YN-565 for off camera reception lighting and I LOVE them. i have several 580s that I use on camera but these are just as big and powerful.
I've used them over the past two seasons and have one go down. It is easier to buy an new one than to hassle with China. Even with that, i will buy more Yongnuo flashes.
Depends what your doing. If have the time to setup and use flashes and meter manually the you don't need ETTL For events and situations where you have less time ETTL is essential. I use a pair of 580EXII and love them.
