... I love the alpha system because it allows users to see what they are getting as they are getting it-even with manual flash. It demystifies flash if you will, and allows for optimal exposure in any setting without having to guess if the meter system is correct- or even bother learning the meter system if you don't want to.
How does your A-mount system have an edge there? You still have to shoot a frame and look at the result to see the effects of flash, don't you... just as you would with any other system?
Turning the flash on, shows the expected exposure.
The camera only shows the expected
ambient exposure (if Live View > Setting Effect is turned ON). If Live View > Setting Effect is turned OFF, it shows a 'perfectly exposed' view of the scene just so you can see it better although that might be completely different from the final result. Finally, neither display tells us anything about the end result of the
flash exposure, which could be considerably different from both of them.
This helps in situations where the flash is needed to get a proper exposure.
It doesn't help judge the effects of the flash exposure at all. You need to take a shot and review it to see that.
Example, if your settings are for -2ev you will see a dark image on the EVF. If you turn on the flash, it will show you a properly exposed image in the EVF.
Think about what you're saying. If Live View > Setting Effect is OFF, the image you see while composing will be one thing, and if Live View > Setting Effect is ON, the image you see while composing could be another thing... but the final result with the
effects of flash included could be something completely different from either of those.
The camera cannot preview that for you.