When comparing CrossBrowserTesting vs Endtest, the Slant community recommends CrossBrowserTesting for most people. In the question“What are the best cloud-based cross-browser testing services?” CrossBrowserTesting is ranked 2nd while Endtest is ranked 3rd. The most important reason people chose CrossBrowserTesting is:
Can automate tests for Chrome and Firefox extensions using Selenium.
Ranked in these QuestionsQuestion Ranking
Pros

Pro Automate browser *extension* testing
Can automate tests for Chrome and Firefox extensions using Selenium.

Pro Free manual testing for CodePen projects
Put your code on CodePen and you can manually test it with CBT from the "Choose a View menu".

Pro Uses real browsers, not emulators
CBT uses real, physical devices for live (manual tests). Check the pictures on their blog post.
Automated tests use real Android devices (Nexus, Galaxy) and iPad and iPhone simulators.

Pro Community / forum
Only 350 users, likely because the Forum isn't linked prominently in the top nav menu and because it uses a crappy engine.

Pro Record videos
Record videos of a URL in the browser/OS combination manually or automatically via the API.

Pro Screenshot comparisons
Automated screenshot comparisons report differences in layout. Manual side-by-side comparison also available.

Pro Selenium testing
Selenium automation for mobile and desktop browsers, using scripts easily recoded with Selenium Builder.
Pro Codeless automated testing
Endtest allows you to create automated tests for web applications, directly on their cloud infrastructure. No coding skills are required.
You can also choose the action "Execute Javascript" for a more flexible test run.
Pro Running your automated tests on their cloud infrastructure
You can easily run your automated tests on their platform, just by clicking the run button.
Pro Designed for Continuous Integration
It has an API which allows testers to run it on Jenkins or Team City. Other than that, it has a built-in test scheduler to allow testers to preset test executions.
Pro Now supports mobile testing
Endtest has added a new feature which now supports mobile testing for both Android and iOS (.apk and .ipa).
Pro Option to export your automated tests in different formats, including .EXE
You can export your automated tests in a variety of different formats, and run them on your own infrastructure. The formats are either in Python file format or executable file format (.EXE).
Pro Now supports a wider variety of browsers, operating system and devices
As of March 2018, Endtest can now support multiple platforms (Windows, MAC, Android and iOS), Operating Systems, and more than a handful of devices for both Android and iOS.
Pro Super fast and affordable.
Pro Premium version is relatively cheaper than most in the market
Their pricing plan ($79/month or $650/year) includes team plan upgrade, which means the whole team, regardless of the number of users, will only need to subscribe to the $79/month or $650/year plan. This includes unlimited test runs, test exports, recordings, etc.
Pro It's mostly free to use
The free plan covers a lot, you can have up to 3 test suites, and you can run your automated tests as many times as you want. The pro plan includes some very advanced options that you might need only if you're working with a team (for example, the collaboration feature, schedule test run, API for Jenkins, etc.).
Cons
Con Slow and unstable

Con Not a sponsor of the Selenium project

Con Typos in the documentation
"relavent", "retreive"

Con Can't change physical iOS device orientation
All iOS devices are physical and arranged in portrait mode. Emulators/simulators and Android devices can change their orientation via a button or keyboard combination.

Con Very slightly misleading Selenium examples / documentation
The Selenium WebDriver script examples, by default, don't explain what to put in browser_api_name
and os_api_name
. This leads to an UnknownError: Invalid browser_api_name / os_api_name combination specified
error, if you just copy and paste the script.
Instead, first select an OS and browser combination, and the script wizard will fill in the '?'s for you.
Con Doesn't support a wide array of browsers and/or operating systems
Because it's still in its infancy, it doesn't yet have a huge variety of browsers and operating systems.
Con Free plan has limited time storage for test suites
If you are using the free plan, keep in mind that the test suites created there are scheduled to be deleted after around 2 weeks. Endtest will send you a notification email the day before mentioning "Test suites from users who are not on the PRO Plan get automatically deleted after some time," and offering for you to upgrade to PRO.
Con Codeless and locks you in rendering your efforts useless if you want to switch
Con Bad UI
