Dunno in all honest Opeth, i went for the CH6 as it was the perceived to be the absolute best board, then 8Pack said the Taichi was close, so i bought one of those also, the CH6 was the winner for me as Elmor @ Asus kept the bios work flowing and it got regular updates etc.
I dont tend to ever skimp on motherboards, PSU, etc hence i have a 1000w Superflower Platinum PSU, and with Motherboards the CH6 and Taichi were the clear winners, however my brother runs the B350 Tomahawk and has never had an issue with it and his 1700.
In all honesty if i was to buy a 2700X theres a good chance i would buy a new motherboard, i would probably look towards Taichi, i wouldnt ever consider MSI, ever, period, they are a garbage company. I had a Gigabyte for my 4770k but given their antics with GPP i would probably not buy any of their products either, so im pretty much left with Asus and Asrock lol, ive had good experiences with my CH6 but i like the aesthetics of the Taichi, my only worry with Asrock is bios support is nowhere near as good as Asus.
To get the most out of these new Ryzens, especially the 2700X i think it would be best to just buy a highend motherboard as they are all designed with the power phases etc to push the chips correctly. Either that or pick up a CH6 to run with the 2700X, personally as i said, id buy an Asrock Taichi and hope they get ontop of bios updates, as the actual hardware design is second to none, they use some of if not the best components when building the Taichi boards, VRMs etc are all solid etc.