The keyboards you get on iOS and Android aren't perfect, but they're what you get so that's all there is to it, right? Wrong.
One improvement is the TouchPal Input Suite, a replacement keyboard for Android. It adds many features over the standard one. On a tablet you might want to "split" the keyboard to the left and right sides to make them easier for your hands to reach, for example.
The Input Suite also has "sliding," which lets you slide your finger from one letter to the next for a word, which might be easier than pressing them. For longer words you will see predictions show up as you slide, so you might not need to complete it yourself. For more on sliding see the demo below.
There are other third-party keyboards for Android, but Apple does not allow such software for iOS, so there are none.
TouchPal's other product is Dialer, which lets you find contacts with a telephone dialer. In this way you would use 2 for ABC, 3 for DEF, and so on. It also predicts so you might need to press only a couple of numbers. Dialer is available for both Android and iOS. Both products are free and have no ads.