I believe they are similar, go for the z270 GAMING M5 there is a guide on bitcointalk.org on building a 7 gpu rig on it -
. In case you encounter any problems when building the rig you can refer to the link and there`ll be many people on this forum willing to help you. Also don`t purchase a intel kabylake cpu, purchase an intel celeron g3900 skylake cpu or higher.
Are they both will make problems running 6 Gpus and I read for MSi z270 to Run 6 Gpus will need to Custom Mod Bios.