[DrKnow65]

hyp7, you need a little battery 101 :-)

"C" rating relates to the batteries current producing ability.
Current being a measure of amps. You didn't post the mah (milli amp hours) of the two examples. The mah is the number you multiply by the C rating to find the amps the battery is rated for.

For example lets say you were looking at a 4S 40C 5000mah battery versus a 5S 20C 5000mah battery. Which one handles more amps?

40C x 5 amp hours (drop the milli) = 200 amps at 4S
20C x 5 amp hours ... = 100 amps at 5S

So, what about watts? (that's the electrical equivalent to horsepower 745w = 1 hp) watts are calculated amps times volts.

Back to our example:
200 amps at 4S (14.8v) = 2960 watts OR 3.97 horsepower
100 amps at 5S (18.5v) = 1850 watts OR 2.48 horsepower

So clearly a 4S lipo at 40C will out perform a 5S lipo at 20C.

That's a 101, you can take it farther into watt-hours and internal resistance, but that's beyond the scope of your question :-)

Welcome to RC Monster by the way ;-)