I’ve not tried the USB connection myself, I understand it’s a bit old fashioned and can be a bit sensitive to what’s plugged in!!
It will read MP3s off a USB stick or it will interfaces with an old-school iPod. It absolutely will not work with a modern iPhone running Apple Music (tried that).
Essentially, it's a waste of space in this day and age.
I personally went for
Pioneer SPH-DA160DAB unit as it comes with both CarPlay and Android Auto out the box. The install is straightforward if you get the Connects2 fitting kit + replacement fascia.
The SPH-DA160DAB has a
capacitive touchscreen (same as your smartphone), which is a bit more reactive to my sausage fingers. The cheaper end of car stereos tend to have
resistive touchscreens which require a bit more force and it's not necessarily a Good Thing to be having to mash your digits into the centre console with max force.
My EX has decent speakers already but it felt like the new head unit made a bit of a difference in sound quality. That and the graphical EQ helps get the sound you want rather than being restricted to MOAR BASS or MOAR TREBLE.