Hyper-V Virtualization Advanced ECC or Optimzed

Hello,

I have a dell poweredge t710 with 64GB of RAM 8x8GB RDIMM as Advanced ECC.

I have 10-Virtual machines on windows 2008 r2 hyper-v. All the hyper-v are running SQL with about 7-users each in them.

Should I be using Optimezed spec or stay at the Advanced ECC best choice?

Also I will be purchasing another set of 64gb of ram 8x8GB too so total of 128GB.

So hyper-v with 128gb what mode should my ram be. the vms are critical data!