When comparing WebdriverIO vs Puppeteer, the Slant community recommends Puppeteer for most people. In the question“What are the best Javascript end-to-end testing tools?” Puppeteer is ranked 3rd while WebdriverIO is ranked 4th.
Ranked in these QuestionsQuestion Ranking
Pros

Pro Works with any testing framework or assertion library
WebdriverIO lets you use your favorite testing framework (Jasmine, Mocha, Cucumber) and assertion library (Chai for Mocha). Other projects implement their own testing and assertion APIs, for example Nightwatch, Intern.
It should be mentioned though that v4.2.16 has an incompatibility with at least tap v7.1.2: stdout/stderr written during a run gets lost.

Pro Used by Chimp.js
Chimp.js, is an emerging web application test framework that implements easy sync tests using WebdriverIO, CucumberJS and Chai. Features include:
- synchronous style
- built-in "widget framework" (an implementation of the PageObject pattern)
- automatically downloads dependencies (ChromeDriver, PhantomJS etc.)
- works with SauceLabs and BrowserStack (CrossBrowserTesting TBD)
- automatically takes screenshots on failures
- works on Windows in addition to Linux and OS X
- automatically produces boilerplate code for step definitions, which you can copy, paste and edit
- file watcher reuses the browser sessions and can run only the tests you tag, to maximize development speed

Pro Excellent API documentation
Pro Synchronous implementation of asynchronous browser commands
So you don't need to worry about promises

Pro Config file generation wizard
Run wdio config
and WebdriverIO will generate a config file for testing locally vs. in the cloud, specifying the test framework (Jasmine, Cucumber, Mocha), where to find tests and store screenshots etc.
Pro Allows you to do visual regression tests using WebdriverCSS
WebdriverIO has a plugin called WebdriverCSS that allows you to do cross visual platfrom/browser tests with an integration to Applitools.
Pro Provides plugins for gulp, grunt and other
WebdriverIO is accessible via gulp and grunt and even has a Sublime Text plugin for autocompletion.

Pro Simpler syntax than selenium-webdriverjs and WD.js
selenium-webdriverjs:
driver.get('http://www.google.com');
driver.findElement(webdriver.By.id('q')).sendKeys('webdriver');
driver.findElement(webdriver.By.id('btnG')).click();
WD.js:
browser
.get("http://www.google.com")
.elementById('q')
.sendKeys('webdriver')
.elementById('btnG')
.click()
WebdriverIO:
client
.url('http://google.com')
.setValue('#q','webdriver')
.click('#btnG')

Pro Used by Meteor's Velocity test runner
If you develop web applications with Meteor.js, you might want to use the xlovio:webdriver wrapper, because it's the Selenium binding behind the preferred testing framework (Chimp) promoted by the Velocity (Meteor's official testing framework) team for using BDD via Cucumber.
Pro Selenium Server need not be started independently
Service is provided by WebdriverIO which over comes the con of starting selenium server independently.
Reference: http://webdriver.io/guide/services/selenium-standalone.html
Pro Works great with modern node.js features
Pro Runs a real browser
Unlike the other options here, this is a real browser, just without the GUI parts. This means the quality of the test is much higher, and lets you do things like save to PDF or images.
Pro Actively developed and promoted by Google
Pro Complete API for Chromium included
Chromium tests depend on the same API that Puppeteer gives you access to, so all the features are included
Cons
Con Must run with WDIO to debug
Tasks written in this beautiful Selenium API can only be debugged using the provided WDIO task runner. You can't set breakpoints within tasks, but you can have WDIO pause the run between Selenium commands.

Con Selenium server must be started independently
selenium-webdriverjs starts the Selenium server automatically, and actually manages to achieve a faster startup time (4 seconds vs. 5.5) than WebdriverIO.
Con Have no docs for latest version (4.0.5)
Con Not good for Cross Browser Tests
Since it only tests via Chromium, it won't help you test inconsistencies between browsers like Edge or Safari. There are projects to get around this, but they aren't mature.
