Migrating partitioned drive with 2 different Operating systems to a new drive

My 2012 MAC Pro HD is failing. It has a partitioned drive (High Sierra & Snow Leopard). I want to migrate all my data and both OS’s to a new partitioned drive. Will Migration Assistant capture the partitions and move both the Mac Os’s and apps/data? I have a separate Time Machine for both OS’s on two external drives.

Since I have 5 internal HD bays would it be better or easier to dedicate an HD to each OS on separate drives? 

Thanks in advance.