Simply from speed/stability, you might be better off on iOS 7.1.2 (assuming you like how it is on it so far), otherwise, for various newer features (if they might be useful to you) and some other improvements and security fixes, it might be worth going to iOS 8.
Of course no one can guarantee that the upgrade will be trouble-free for you or that you won't run into some issues with iOS 8 that are worse for you than iOS 7, given that it's different for everyone. But in the overall sense, it should be fine if you go with iOS 8.