Going for 16GB storage on my 5S might be what makes me upgrade...otherwise the phone still seems fast / good enough for most tasks after 2.5 years of ownership.
I bought a 5s recently (iPhone 3G -> iPhone 4 -> Nexus 4 -> Moto X 2013 -> Moto X 2014 before), because I had too many problems with Android. Mine feels incredibly snappy.
Maybe I'm using the wrong apps.