Last part 1st, I think the 2 biggest reasons to create DVDs is that they're common & they work. You can create Blu-Ray discs, but you probably won't want to share them widely with friends & family -- billions of people can watch DVDs, & while millions can watch Blu-Ray, most people can only use them in their living room with their HDTV. You can give them video files of course, then play at tech support when one or more people can't play it, and then figure out how to get them not to hate you when something goes wrong with their PC/laptop -- of course you had nothing to do with it, but good luck convincing anyone.
At home for your own use DVDs are arguably the cheapest way to store video files, whether you burn several AVC files to a Data DVD or create a video DVD. The mpg2 video DVDs use isn't as efficient a format or codec compared to AVC/H.264 [or the newer H.265], but it's much easier to encode & play. And regardless what you see on retail video DVDs you buy, rent, or borrow, mpg2 is capable of storing video with the same quality as anything else, including AVC -- it's very common for Hollywood & such to put lower quality video on a DVD because people have been trained to accept poor quality, plus they feel it doesn't hurt theater revenues as much, plus they feel that the lower the quality, the less to fear from piracy.
The downside to mpg2 video is that the files are bigger, but that only matters if you're storing the video on your hard drive(s) -- once they're on a disc & off your drive, what difference does the file size make? Yeah, you may fit 4 hours of AVC video on a DVD, whereas you'll max out at 2 hours on a single layer video DVD, but at less than $20 for 100 DVD blanks, how cheap are you? :) Another downside to video DVDs, & an inescapable one, is that they're not HD. If you've got really high quality HD it probably deserves better than a video DVD can offer, but that said, really high quality HD in the home is somewhat rare [at least legally]. HD is common -- high quality HD is not. What you get via broadcast or cable or satellite is not high quality, & most people don't spend over $1,000 on a camera so they can shoot high quality HD. Now I'm not being elitist, but practical -- few people can tell the difference between average quality HD on a Blu-Ray or the same video downsized & placed on a video DVD, *as long as the conversion to DVD mpg2 is done properly with highest quality*.
OK, that's playing advocate -- as I said: "Why Create a DVD". Loads & loads of people on-line will gladly proclaim any sort of video on an optical disc as an ancient relic from some dark age long past. Hmmm, and this is where I bite my tongue as I think about what many of these same folks put up on F/Book or tweet. A couple of downsides to having all these .mkv &/or .mp4 files is where do you put them & how do you watch them. USB sticks & external drives work but the costs add up unless you pull old video off to put new video on. That's a drag, so many people have turned to on-line streaming. If you're OK with the subscription cost, the titles offered, often so-so quality, & the frequent lack of subs or captioning, streaming is probably pretty cool. Another way to do it is to have centralized, networked storage. As long as you have your home wired, with network access wherever you want to watch that video you're cool -- you shouldn't plan on WiFi delivering high quality HD. Like most people I'm not a fan of converting video for a tablet or cell, just so you can stream from that device to your TV -- Way too much work, often questionable quality, & always too short battery life.
Do Not use a video DVD if your video is smaller than 720x480 or 720x576 -- you can still put it on a video DVD but probably shouldn't, & in fact you shouldn't re-encode it at all, as there's usually not enough quality there to withstand the generational loss you get whenever you re-encode. If you must, you must, & then you should use software that will let you avoid re-sizing the video -- there's a fair range of video sizes that are in the spec. It's much better though to leave smaller video alone, storing it as-is or pulling the content out & sticking it in a more compatible container like .mkv or .mp4.
