VMware ESXi and RAID groups sizes

Let me start this off by saying I am not a SAN administrator, I am the VMWare guy that got put in charge of the EMC SAN we recently acquired, the CX4-NS480. It has the latest FLARE version as of January 1 2012 and has Unisphere 1.0.0.17. We are using 300GB 15k FC drives.

We are currently in the process of moving some of our VMs to the NS480 from our current HP MSA and EVA SANs.  I have been reading a lot of documentation, best practices etc. and currently have a few questions regarding the size of RAID groups recommended for VMware datastores under different use scenarios which are listed below.

Large number of light load VMs that do little disk activity ( Daily average of a few KBps)

Moderate number of medium load VMs that do little disk activity ( Daily average around 80-100 KBps)

VMs that perform a large number of reads and very few writes (80-90%+ reads 1-2 MBps)

VMs that perform both a large number of read and writes(50% reads, 50% writes 1-2 MBps)

VMs that have little activity through the day but large number of reads at night (backups)

I have read that creating several 4+1 RAID 5 groups and using meta LUNs would be better for read intensive VMs and having a larger 8+1 RAID group is better for write performance. Is this true or are there other recommendations for creating RAID groups?