Panasonic BK-4HCCA4BA eneloop Pro AAA New High Capacity Ni-MH Pre-Charged Rechargeable Batteries, 4 Pack

Q: If I use these for photography flashes -- why would I use the pro version instead of the regular ones? I'm confused as to how they are better

The Eneloop Pro have a higher capacity than the standard ones (roughly 2,450 vs. 1900, about 29% greater); all other things being equal you will get more flashes per battery change. Note that different generations have different performance ratings. In some cases the Pro are rated for fewer charge cycles, however; the Lite versions when available have even less capacity per charge, but more charge cycles.

Q: Are there any differences between this charger and the NC-MQN06U not in terms of form factor but in terms of functionality and charging ?

The new BQ-CC17 charges each cell independently. The old MQN06 charges in pairs only. Other than that, they have exactly the same charging current (hence charging time).

Q: Can the charger be used to charge other brands of Ni-MH batteries. A little tired of each brand claiming only their charger will do it properly.

Yes, a Ni-MH battery is a Ni-MH battery. They say that their charger can only charge their batteries because of legal liability reasons, and so you'll but more of their batteries after you buy the charger ;) Most chargers can detect when it's fully charged because the voltage drops a little when it is, as in 5 mv to 10 mv. The percentage of how much power a battery has is from the voltage. e.g. the peak voltage of most high capacity Ni-MH batteries is between 1.45 to 1.55 volts. I know it says it's nominally 1.2 volts but I think that's when it reaches 0% just like a lead acid batteries in vehicles, they're fully charged at 13.2 volts even though they're called 12 volt batteries. I don't understand the world! I mean a smaller number for gauge means it's thicker?! That doesn't make any sense at all! D: I like turtles.