Ideal LVM2 Extent Size for VMFS on SAN?

What is the ideal LVM2 Extent size, if not the default of 4MiB, when running EL5 as a guest under VMware ESX 4 or 5, using VMFS and SAN storage?

Are there any considerations based on VMware ESX VMFS extents?  SAN allocation?  Etc...?  Anything that may affect this, or factor in?

I assume storage alignment on the LVM2 Extent (e.g., 4MiB) is a given.  But are there any others?  Or do people fall back to 1MiB?  Increase to 32MiB?  128MiB?  Other?

My client seems to be using 128MiB by default for bare metal, local disk (2.5" SAS).  For VMware VMFS on SAN, I'm suggesting we fall back to the 4MiB default.

Wanted to see if there are any recommendations others have, or any factors that would cause one to use anything but the default 4MiB.