Relative performance of writing locators in PageObjects or Properties files

Question

I was going through an Automation Framework that follows Page Object Model but is a bit unstructured. It grew over the period of time and now has around hundred of tests running. While running through the framework, I noticed that some QA had followed writing the webpage locators in the properties file and other in the pageobjects itself. So I was wondering,

How the performance of the tests will vary in bigger test suites(say 1000s of test) if webpage locators follow the different declaration in Java as below:

1. In Properties file(s)

Storing the locator using the properties file and then referencing them.

loginBtn=login

driver.findElement(By.id(prop.getProperty("loginBtn"))).click();

2. In seperate Locator class(es)

Storing the locator using a dedicated locator class and referencing them.

By loginBtn = By.id("login");

driver.findElement(locators.loginBtn).click();

3. In PageObject class

Storing the locator using pageobjects classes itself and create a By object for every element.

driver.findElement(loginBtn).click();

4. In Page Factory

Storing the locator using page factory and initializing it.

@FindBy(id="login") WebElement loginBtn;

I would appreciate if someone can provide a detailed performance analysis of these strategies and in what situation can we prefer the either of the above strategy.