NAS, no question - cheap, supportable (high WAF), easy, much more flexible in usage. In such decisions it is all where you want the brunt of the work happening (on the server itself, on consumers, etc). if you have very stupid and low power consumers (i.e. some $50 android Chinese knockoff tablet) , then server is the only thing that could transcode. if you have consumers with some power (NUC or set up box like Nvidia Shield TV) or run Kodi locally , all 'server' need to do is provide the file and the server part of that is really not necessary.
Questions for you
- do you have or planning to have other media consumers (ipad, etc)? I thought it would be silly to watch media on a tablet, but sometimes it fits the bill greatly vs going to living room for TV, if all you want is finish watching a particular episode on the series. very convenient as an option
- how many people would consume media (anyone besides you) and what is their tech level? i.e. for me, any technology has to be usable by non-techy (Wife Acceptance Factor- WAF) and it is so much easier with voice search and real remotes vs keyboard hacks and plug this thingly into that thingly and run this command and then you can type instruction.
Here how the evolution usually goes
- person (usually guy) starts single with single computer to do everything, gaming, browsing, media serving, media consumption, etc
- then a desire to watch media on nicer TV set up appears, welcome KODI or its equivalents (openelec, etc) and welcome to all of the headaches with proper remote, plugins, etc.
- then other people join, other devices, kids come. f%cking with KODI settings becomes tiresome , and decision is made to centralize all media and expose it through things like Plex to whatever device wants it. person becomes aware of 21st century features like voice control and voice search, time becomes more valuable then saving $100 on such DYU build , and experience/wisdom of having to repair these things vs just buying and having it work finally gets to a person
- data moves to low power, feature rich server (aka NAS) . Almost all of the NAS boxes have built in media streamers (DS Video for Synology as example)
- consumers become better in user experience, things like good controllers out of the box, voice search, excellent experience makes Kodi look like bad dream.
so if I were use I would go out and pick one of the major NAS vendors (QNAP, Synology, etc) , I myself use and happy with Synology but there are many alternatives. for $170 I get a barebone server with multi HD support, with cloud integration capabilities, with built in management apps on my Ipad , domain integration if I want it to SMB/NFS/FTP/etc support if I want it, low media consumption, QAed OS that someone else cares for , excellent and simple backup capabilities, low power consumption. of cause it does not have the full flexibility of x86, I can not run things like virtualization ,etc. but in its class for its needs, it is very hard to beat
then, think of your media consumption experience - for me I moved from homebuilt devices to things like Shield and similarly have not looked back. I can still run full Kodi/SPMC if I want to but no longer driver wars, updates, patches, user experience is excellent, and it could be your Plex Server (actually transcoding for the rest of consumers, while having the data on NAS) if you want it to be.