The concept of maturity is about behaviour.  In essence, the greater ability to respond to the environment in an appropriate manner, the higher level of maturity.

Maturity responses are generally learned/ experience based rather than instinctive or emotionally driven.   Mature behaviour is reasoned and results are usually positve.

Capability and Maturity

The ability to perform effectively (skill/capability) does not in and of itself equal maturity.  That being said, mature actions require capability to execute.

Ability is easier to measure objectively.  For example a high jumper who has the ability to jump higher than all others in a particular competition is clearly demonstrating strong ability.

If their winning high jump is followed by a dropping of shorts and waving a bare bum at the crowd in a victory salute, many might question the maturty of their behaviour.  On the other hand a slight bow and gracefull acceptance of the applause might be considered more mature.

Both these assessments of matuity level are subjective,  based on perceived acceptability of the given behaviour.

The Value of Maturity

Albeit a subjective assessment, on the whole,  mature behaviour coupled with average or better capability will generally produce better results.

The principle basis for this derives from the fact maturity is experience based (i.e., learned behaviour) and so the results are predictable.  That is based on past experience you know what to expect.

Maturity does not just apply to individual behaviour  but can be applied to a collective whole.  As a group behaves at a higher maturity level the results improve are more consistent and sustainable.

Sadly even with a wealth of experience, behavioural maturity can still be average or even low.  Maturity is gained through experience but having experience does not necessarily mean your behaviour is mature.