performance wise use RAID10.
Also create as larger volumes as you can e.g all disks in one array (bear in mind the 2tb max datastore limit with ESX)
This will allow one VM with heavy disk activity to read from all disks for the fastest performance if other VM's aren't heavily using disk.
Splitting it just halves the performance and forces some segmentation for little point as you also half your throughput for each RAID array.
Typically if you are not pro actively managing your disk IO then just lump together as many disks as possible and let the hypervisor handle the load balancing/prioritisation.
4.1 of vsphere has also been hinted to contain tools to prioritise disk access for particular VM's should you want to do so which may well solve your problem in a different way.