As to frequency of updates.........Firefox, like IE, uses directx for rendering and directx is notorious as being the number one weak link in any system or program.......the developers are forced to play catchup frequently and issue patches by way of updates as these weaknesses are exploited by the nasties.
Chrome is not really a browser, although it is being pedalled as that at the moment. Chrome is in effect a beta version of a nascent operating system and like all beta software will be subject to frequent tweaks, changes and developments.
By using Chrome, you are acting as a guinea pig for the dreadful Google organisation.
Opera does not use directx and is a final program in it's own right.