I used to use SwiftKey but it became untrustworthy. Its predictions are now so gnomic that you have to look at it all the time to correct the mistakes. This really slow you down and thus defeats the whole purpose of swiping. Gboard, however, is rock-solid. I love that most punctuation is just a long-press away on the letter keys and you can have a numeric line on top. Also it puts a space and a capital letter after a full stop (aka a period). If you pause after you swipe your word it inserts a space and really speeds things up. Top tip: press and hold the full stop at the bottom right; you then get access to a whole raft of punctuation characters. There is no need to switch to the alternate numeric/special characters keyboard. Best thing? You can set it up in a dark theme.