I'm giving the nod to the DDR4 system as this is almost all brutal CPU and RAM bit slinging.

I would not skimp and get that 120GB. 240 to 256 GB SSD are just a little more and you won't waste your day trying to keep the 120 clean.

Many of these edit machines setup RAID 0 for the big data drives. Then for backups, simple(?) USB drives.