We may not observe much difference while deploying Vsphere 5 except increased resource support for VMware VMs ( 32 vCPU & 1 TB RAM per VM maximum)
But there are lot of new features & enhancements . ( It may depend on the license which you choose as well ) . below listed the significant features in Vsphere 5
1.Storage DRS
2.Storage I/O Control for NFS
3.VMFS-5
2.Storage I/O Control for NFS
3.VMFS-5