Upgrading from 6.6 to 7.2/7.4 - xfs or ext4

I'm currently running a RHEL 6.6 on my production server. The OS is installed on an SSD drive using the ext4 file system.
In addition to the OS drive, I have mounted a RAID, also formatted with the ext4 file system.

I'm now going to do a clean install of RHEL 7.2 (or 7.4) and want to know if I should stick with ext4 on the OS drive or if I should switch to xfs. The new OS will be installed on a new SSD. Any suggestions?

If I switch from ext4 to xfs, will there be any issues in mounting the ext4 based RAID?

Thanks.