What are the advantages and disadvantages of the following?

I have a MD1200 unit with x12 3TB drives. I need to create four volumes. Should I

1. Create 4 RAID-5 groups (3 disks for each set) then add this volume to the attached server or

2. Create one large RAID-5 group and create 4 windows partitions?

What is the trade offs? One of our MD3200 units was configured like this, with x4 RAID-5 groups. Not understanding why it wasn't just wont RAID-5 group, then four partitions.