I think a straightforward server only system could do well with unraid or freenas. Both require you copy all your data to new filesystems though
I still use and prefer a windows server. I am running W8.1, but could be almost as happy with 7. Either way, I like the option for WMC and serverWMC to run on the server. I also run a few other programs like couchpotato, headphones, and sickrage which could be run just as easily in linux but aren't obtrusive to windows whatsoever. There's also uTor which is my preference for clients of it's kind anyway, and it's multiplatform as well. Most things I would like to run are available in Windows. For a couple years I really thought I needed multi-threaded sharing (NFS) so I thought of running WHS or WS since they offer NFS/SMB sharing side by side (on the same shares) or switching to linux. I did run a linux server for about two days, but I couldn't get networking steady and I was in over my head for fixing issues between the rest of the windows boxes and the linux server. I've never seen others have that issue with prebuilt style systems like FreeNAS or unRaid, but if you roll your own ubuntu server w/ zfs every problem gets into the "You have to know everything before you can fix anything" mode of troubleshooting. It's the wild west, and I find it totally manageable from a client/laptop perspective. It was not totally manageable for me at the time as a server. That was really my first "dedicated server" which I quickly re-installed with WHS. That lasted about a month and began annoying me to no end as well. Too much stuff was too hidden for me to configure the way I wanted even for something as simple as controlling the number of image backups it makes for windows clients. Rev3 was really W7, but not long after I updated it to W8 pro for $40 while WMC was still free. I clean installed it of course
I'm now running w8.1 w/ Flexraid's tRAID. It's the most stable it's been through the whole journey
If you choose w8.1 you at least have hyper-v if you want to play around with stuff. There's virtualization software as well, of which my preferred is vmware (their freeware "Player" works nicely for just playing around though I used it to run Sick, Sab, Couch, and headphones from source 24/7 for well over a year with no real issues other than me needing to manually shut it down before windows update shutdowns)
I'd still like to add something like Blue Iris or an android friendly model that works with old android phones running some app. Home automation is on the some day list, but I don't know what's available in that space yet