Good points raised.I'd think heat dispersion and airflow both play a heavy role in overall cooling as does componenet location/placement.
A bigger case affords more heat dispersion area,allowing expelled component heat to dissipate more,hence cooling in the process.Good airflow,expecially exhausting the expelled heat is important too though.Don't wanna let it just disperse and hang around in the case to be reintrodued to the fans' intakes.
That's where component placement comes into place.Components placed in the "line of fire" of airflow will have their expelled heat rapidly drawn out of the case by the exhaust fans.The trick is finding a case that reflects all of the above criteria.
Starting with a larger case would be logical.Then narrowing it down to one with decent airflow,preferably 120mm fans.Lastly component placement would come into consideration,much wich can be configured by the user him/herself.