Difference between priorities and dependencies

Hi,

I have four VMs that depend on services of thee other VMs, all are on one datastore and included in one recovery plan. Should I solve this with priorities or dependencies?

What's the difference in processing priorities and dependencies?

Let's say the three VMs have priority 2 and the other four VMs have priority 3. When will SRM start the VMs with priority 3? Is it when SRM detects that all VMs with priority 2 have VMtools up and running?