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I have a 580EX that needs a flash tube at a cost around $195.00. I can get it repaired or buy a 580EXII for around $360.00. Is the newer model worth the extra? $195.00 into an old flash is a lot to spend but little compared to a new one.
I'd fix your old one. The EX II adds weather sealing at the flash foot, which is a mixed blessing; sometimes the flash won't seat all the way into the shoe which can cause ETTL failure. (If you're in Manual, the center contact is big enough not to be affected.)
Also, the EX II doesn't have the nice Off/Master/Slave lever for wireless mode selection; you have to go into the menus.
The EX II doesn't whine when recharging, but the EX whine isn't enough to bother me so no big deal there.
The EX II also has a built-in autoflash sensor, like on my Vivitar 285HV, but usually if I'm not using ETTL I'll be using Manual flash, so -- again -- not a real advantage for me.
The only advantage of the EX II over the EX for me is that it can be controlled from the camera menu on newer bodies. (In order that I don't have to mess with the flash's menu, I keep my EX II set for Master mode and only use it when I'm doing multi-Speedlite wireless setups. If I'm only using one flash, I use my older EX (or my 430EX II) instead.)