TheSeekingThe RU-6 is supposed to be richer and smoother. Sounds great without having to tweak anything.
The Qudelix 5k is supposed to be a step back in quality and a bit more strident, but still way better than an Apple dongle, plus Bluetooth mode, microphone, and a nice app with tons of DSP/EQ features. Great if you like to tweak things and save some cash.