Mix of both, used them all at one point or another and seen plenty of other users experiences along with a lot of DLNA experience.
D-Link is probably the worst option for Samsung because of their lacklustre in-house UPnP server, they are up their with Buffalo and Western Digital in not being keen on running other programs on their NAS at least not easily, you can find plenty of advanced hacking for most NAS and it's possible to install Twonky 7 (latest version) even on the old D-Link DNS 3xx series. I believe someone has even managed to get Serviio running on those too but it's not something for your average user to easily pull off.
The deluxe NAS are Synology, QNAP, Asustor, Netgear (only their latest stuff) and Thecus, these all allow the packaging of apps that make it easy to install on the NAS so you can replace the built in DLNA media server with something better if you need to and not have to be a full on linux guru either.
Zyxel make decently cheap NAS too, I think they use Twonky and keep it up to date or so I was told but I haven't checked on that.
Serviio is the very best option as your preferred DLNA server if you can get it, lots of features and plenty of settings to give you exactly what you want. However it also requires Java runtime and needs a little more processing power but most entry level NAS that can run Serviio already meet these criteria (at least models from the deluxe vendors). Serviio is good for media libraries or just raw folders (think browsing network shared folders), whichever layout floats your boat.
TVMobili is also a good DLNA server, ideal for low end systems and not as resource hungry as Serviio, TVMobili isn't as good for media libraries but is good for raw folders.
Plex doubles as DLNA server and of course has it's own Plex clients, not recommended for low end systems (anything Arm or PPC), works best with x86 based NAS, Plex is very resource hungry and CPU intensive. Plex is great for media libraries but bad for raw folders.
Twonky is a serviceable DLNA server that's been around a long time. The people who make it are horrible to deal with and the server is just not that well featured, only good for raw folders but it doesn't even get that right with very poor levels of customization. Lot's of low end commercial NAS have Twonky and they are rarely updated to the current version.
Last edited by Alx330; 06-17-2014 at 12:55 PM.