If you are aiming to upgrade for the i9 9900k later , do not go with any.
Either
MSI GodLike Z390
or
ROG Maximus Z390 XI Extreme (Which I personally have chosen for the i9 9900k)
Overclock.net have compiled a nice list including the VRM stages / Quality and divided the z390 boards into tiers.
As the Voltage phases increases with the amp per phase results in a better overclocking stability / less heat the VRM , less tolerance to power and/or thermal throtelling.
Other wise ,
Difference between Z370 vs Z390
Native USB 3.1 10Gbps Data Ports
Integrated Wifi on the Chipset
Source: Anandtech
Since the price difference between the z370 & Z390 is slim, I will definitely go with any z390 board now & later upgrade. For the i9 9900k OC / i9 9900k non OC upgrade plan as I have mentioned. Otherwise of anything from i7 9700k & downward a good z390 board is sufficient.