Which flash for EM-5

I have posted this as a question but it doesn't seem to apear anywhere so here it is again.

Hi guys,

I am about to decide for a flash for my new EM-5 and hesitate between FL-50R and FL-600R.
I really do not need the video light and prefer the more powerful model.

My questions are:

1. does the FL-600R have any other advantage except the video light compared to the FL-50R?

2. is it possible to use an external power pack on any of them?

thanks in advance,

Moti

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