As you would expect from Adobe, the interface and user experience of the Photoshop Express photo app for Apple and Android devices is faultless. It fulfils all the functions you need for picture editing and will probably be the one you turn to for sheer convenience. Straighten and Flip are two useful functions not included in many other apps.
However, none of the filters really jump out, and some are surprisingly naff for an app that comes from the developer for designers. Ultimately, if you are looking for a more professional tool, look towards Lightroom CC for mobile, but the cut-down feel and familiarity of PS Express will suit some.