ERP OS/Database

I am part of a team evaluating several ERP solutions and I would like to hear from anyone that has an ERP (any one) about what Platform/OS/Database they are using. Our management is dead-set on using Oracle on OpenVMS, but I cannot see any compelling reason to use it over either a Windows or UNIX solution. Actually, I have not been able to find any ERP vendor that implicitly supports OpenVMS, although you can get Oracle on OpenVMS.
That may be, but my argument continues to be that if no one else is using it, why should we?