Capacity? Performance? Flexibility to set things up the way you want it?
I tend to always try to do things with a real server abd avoid appliances as much as possible, including even more Enterprise oriented brands like QNAP.
Whenever I can use server hardware, I do. Even my router is running on PC hardware with using pfSense.
Also, IMHO, it sounds like a really bad idea to out your storage on the same device that is your WAN bridge and firewall.
My storage server has 2x 8c/16t xeons 256GB of RAM, 12x 10TB hard drives, 8x SSD's in various caching etc. purposes, and dual 10gig Ethernet adapters.
I can probably get about 2GB/s reads off of the hard drive storage array, and it supports a lot of stuff I do in my home.
Can't do that with a raspberry pi.
Sounds fair enough. I only asked as an educational exercise because, given my use case, I couldn't conceive of needing to dedicate an entire PC build for a file server as the most demand I ever place on my network storage would be an occasional Bluray Rip, Steam Backup, or system image transfer. It would seem our needs are vastly different considering you went a step further by employing enterprise grade servers. There's no way I could justify that for my 1 bedroom apartment lol.