There are a lot of keyboard apps on the Google Play store. Many will have a relatively standard layout for the letter keys, while others claim that using a new layout they developed is faster. Unfortunately, the only proof they really give you is their practiced videos -- which aren't going to showcase any flaws in the typing. If you've got a serious interest in how fast the keyboard will allow YOU to type, then check out Typist.
With the Typist app, you can time your wpm (words per minute) with a selection of typing tests and duration settings. The app will keep track of your scores, and allow you to compare them to the scores of your friends on Google+. Let's get started:
First you'll want to grab a copy of the Typist app from the Google Play store.
Before you set up your Google Games connection to see the scores of your friends, you may want to try out a few typing tests. Make sure you adjust the time length you want for the test (1-3 minutes), and you can pick a random or specific letter-labeled test from the drop-down menus.
The timer is paused until you start typing, but once you do, don't stop! If you make any mistakes, they will be highlighted in red. While typing, you can and should correct errors.
Once finished, your wpm score will be displayed. You'll be prompted to save it (which you can also delete with the x in the top right-hand corner) with your name, arcade style. Swiping across the scores will let you see your average wpm, along with a graph about your typing accuracy and errors.
If you're ready to see how your scores compare to your friends, you can tap on High Scores from the main menu, then Show Leaderboards. This will prompt you to connect the app to the Google Games service. Make sure to adjust the permissions that pop up for Google+ to best suit your needs. If no one in your selected Google+ circle(s) has played the game, you can check out the public tab, instead.
After you've done all of the tests and can maintain an average score, you can switch keyboards on your device. Then it's time to see how the claims of that keyboard hold up when someone who doesn't work for their company is using it.
Keep in mind that Typist can only provide a speed result that is relative to what you're typing. When composing a message, you're going to know what the next word is, and may reuse many of your daily phrases -- making your speed rating higher. And if you're using a learning keyboard that will insert the next word for you, the wpm is going to represent how fast you can tap the next full word from the top line of the keyboard. In some cases, it might be beneficial to know if using this method actually is faster than just tapping out the whole word yourself.