When they refer to C they are refering to the Capacity of the battery.
20C and 25C is the amount of current that they can supply constantly.
Demon 5 x 20 = 100A
Orion 3.6 x 25 = 90A
You will also see them refering to Sustained (usually 30C on a 20C pack) and Burst (approx 50C on a 20C pack).
You have to take into consideration that most of this will come from flight where they have more constant loads and know how to calculate what they will need capacitywise.
The higher the C rating the more of a premium you will be charged - 20C will be enough.
I bet they'll be in at Speedtech this week. Kyosho said they were in a container, crossing the ocean on the 15th of this month...so...soon...very soon. That -- and they haven't changed the due date at all. Like I said, they left from Korea already.