Depends on the game. Shooters are great with regenerating health in my opinion. Other games such as Skyrim or Mario/platformers do well with a health bar that requires pick ups and such.

Health numbers over/next to your health bars!

You have the accuracy of an exact number while also being able to just take a quick glance at your general status.

Hit points can express a far greater (or more accurate) number than a health bar can.

On the other hand, the bar is more readable in situations that require more impulse actions and less cognitive actions.

I prefer cereal

Pokemon does it right. We need both.

no, well. Now it is sort of. 

before this generation, most every wrpg used Dungeons and Dragons a Paper and Pen RPG rules. Which is quite complex with Attack, Dexterity and modifiers, which featured dice rolls etc. Old games like Neverwinter nights, showed math equations in a log while playing the game.