The deeper the order books, the more stable a currency will be.
Well that is also true guess it would depend how much money is around a price range to make it move up or downward that would make a currency or Bitcoin stable, but by market cap is the question ^_^.
True, but market cap can a coin make more instable!
Think about a highly valued coin with very thin market books. If someone wants to cashout a chunk, the market will tank.
The same cap with highly liquid markets would eat up that sell in seconds!