How to properly use metatables as classes?

So recently I've been using metatables to behave as classes pretty frequently. I read, however, that whenever a table is indexed in lua, it checks to see if the index is nil in the original table first and then references the metatable. Does this mean that it would be more efficient to create a new set of functions for each 'subclass' and abandon metatables since I do not need to update class functions dynamically? Or would that be a waste of memory?

Here's a better demonstration of what I mean to say. Which of these methods is more efficient for making classes which do not need to share data or dynamically change?

Metatable:

local cas = game:GetService("ContextActionService")

local Action = {}
Action.__index = Action

function Action:new(name)	--class constructor

	local action = {}
	action.name = name

	return setmetatable(action, self)	--Each subclass has table Action as a metatable and shares its functions
end

function Action:Bind()	--example function

	cas:BindAction(self.name, self.Handler, false, self.binding)

end

Constructor Function:

local cas = game:GetService("ContextActionService")

local function newAction(name)	--class constructor

	local action = {}
	action.name = name

	function action:Bind()	--example function, each class has its own copy of the function

		cas:BindAction(name, self.Handler, false, self.binding)

	end

	return action

end

My guess is that metatables are only useful for class structures when the subclasses have to communicate with each other, and so I should use the second method when possible to maximize read time.