My problem with the stock keyboard is
1. The low contrast color makes it difficult for me to see and read. Especially the predictive words.
2. I have had an issue with email addresses popping up when I don't want them. It's irritating and annoying. I've tried deleting all my shortcuts and starting over with better shortcuts. That didn't work. So I reset the Dictionary Keyboard in Settings. That did not work. The email addresses keep popping up as like auto correct words. SwiftKey does not do that. So SwiftKey it is. And I really like it better.
Sent from my ancient but trustworthy iPhone 5. ☮