When comparing TestingBot vs Endtest, the Slant community recommends Endtest for most people. In the question“What are the best cloud-based cross-browser testing services?” Endtest is ranked 3rd while TestingBot is ranked 11th. The most important reason people chose Endtest is:
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.
Specs
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Pros

Pro Runs Selenium tests

Pro Appium support

Pro Secure tunnel for testing code locally

Pro Run tests in parallel

Pro Allows testing both manually and automatically in several browsers and platforms
You can test your website both manually and automatically with TestingBot in different browsers and platforms.
Pro Pristine VM for each test
TestingBot guarantees a fresh, untouched virtual machine for every test, unlike with browserstack
Pro Free for 100 minutes
Free accounts receive 100 minutes free manual testing, paid accounts have unlimited manual testing minutes.
Pro Latest browsers (beta/dev)
You can run tests on the beta/dev builds of browsers, to make sure everything works on upcoming browser version releases.

Pro Real mobile devices
TestingBot now offers Real Mobile Devices in its datacenter, capable of running both automated and manual tests.

Pro Manual testing
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 Uses mobile emulators instead of real devices
Unlike CrossBrowserTesting, TestingBot uses mobile emulators.
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
