While I'm all for NAS based solutions (LeftHandStorage, Netgear, Drobo, Thecus, QNAP, etc. etc.) I'd first ask what is "real-world" environment to you? How many concurrent VMs do you plan on running, what OSes, what roles (email, web, file), blah blah blah.
Second if this "real-world" production environment needs high availability, would you risk using SATA disks vs. SCSI or SAS (assuming both models you listed are SATA)? I'd sleep better at night with SCSI or SAS.
From the information you've given, if you have the opportunity for FC in an HP DL380, I wouldn't hesitate for FC. If you can afford it, maybe two FC controllers for failover, but the pure bandwidth alone from FC is too good to pass up and the DL380s can hold up to 12 disks (I think) which is more than either one of those NAS devices.
I don't have any experience with OpenFiler (yet) but I'm sure that it would suffice for all your storage needs.