Partition Vs Volumes .. Which one is better?

LVM (Volumes) in general is far more powerful and flexible compared to the older partitions model. One thing that I believe the F5 does with LVM is dynamically generate volumes for things like mysql, when you switch provisioning roles, and also for installation targets. I haven't tested thoroughly, and they may still want you to reboot.

Also, depending on your provisioned modules' needs, you can delete installation targets to run certain combinations of modules (creating available space for them), but this can get you into trouble if you're not careful.

I believe that on VEs a second disk can be utilized based on the provisioned modules, with LVM behind the scenes making it very easy.