Best Format to Rip DVD for Quality/Size/Plex, etc.

Know the Format of the Disc

Commercial discs store movies in the highly efficient MPEG-2 compression format. MPEG-2 images have four times the resolution of MPEG-1 images and can deliver both interlaced and progressive-scan content. Due to different frame rates and resolutions, DVDs is encoded in MPEG-2 in either NTSC or PAL standard. MPEG-2 is a lossy video compression method that is not as efficient as the H.264 or H.265, to reduce the overall size of the video data.

E.g.:
MPEG 2 (DVD quality) -> approx. 3.6 GB per hour of video.
H.264 (720P) -> approx. 1GB per hour of video.

Note: Anyway, you should know that DVD format MPEG2 has quality loss when a disc is made. Therefore, you can't go lossy-to-lossless DVD conversion [Can you rip a DVD losslessly?]. But you can archive your home DVD movies on the hard drive without further quality loss by extracting the intact content from DVDs.

Best Format to Rip DVD for Quality - ISO, MPEG2, or Video_TS Folder

ISO image file is a single file that contains the entire content of the DVD, CD, or BD, including subtitles, extras, videos, audio, menus, etc. ISO image is an uncompressed and sector-by-sector copy of a disc. It's the best format to rip a DVD for archiving purposes with 1:1 quality & size. It can be played on most video players like VLC and easily allows users to burn it to another DVD with full quality. To build a digital library exactly same as DVD collections and play the movie as you're playing the disc, use ISO image [check how to copy a DVD into ISO image]. Note that the ISO image is large in size. 

Video_TS folder, same as ISO image, is also 1:1 DVD copy. But it's not a single file and contains all the DVD information with IFO, BUP, and VOB files. The  VOB files include the actual video and audio, subtitles, and menus; IFOs are information files or directions that the DVD player uses and the BUP files are backups of the IFO files. It's a format to archive a digital and playable DVD on the hard drive.

MPEG2 is the video codec used in the DVD with linear PCM, AC-3 or DTS audio within the VOB wrapper. It's also the best video format for DVD conversion when you want the DVD only with original quality. This is because when you rip a DVD to MPEG-2(.mpg), you will have the full video, but lose any extras, including subtitles, hidden files, adverts, alternative audio formats, etc. 

Best Video Format to Rip DVD for Plex

Some people are ripping DVD for easier playback on TVs and other devices via Plex media server. Plex won't support VIDEO_TS, ISO image, BDMV or other DVD-type files, so users can't play DVD 1:1 on Plex. The formats supported by Plex include ASF, AVI, MOV, MP4, MEPGTS, TS, MKV, and WMV. You can rip a DVD to any of these formats. But if you have to ask which video format is the best to convert a DVD for Plex, we will recommend MKV.

MKV supports almost all the audio and video compression formats and offers a plethora of extra features like subtitles, menus, multiple video and audio tracks and chapters. It also has high quality and more future-proof compared to MP4. By the way, you can easily rip DVD for MKV format for Plex or other players using Handbrake and MakeMKV.

Best Format to Rip DVD for Mobiles

Different devices support different formats. What's the best video format for archiving & playing DVD movies on phones & tablets? It depends.

* iDevices: MPEG-4 at 640 x 480 pixels and H.264 at up to 720p on most iPads, and up to 1080p on the iPad mini and iPad Air. You can use Apple's MPEG 4 video container format MOV or other H.264 formats for the DVD conversion.
* Android: the format supported by Android mobiles is H.264:

Rip DVD to a Format with Best Quality and Smallest Size

ISO image, Video_TS folder, MKV all provide full DVD quality, but also very large size. For example, the ISO image file ripped from a 4.7GB DVD can also be GBs in size and MKV ranges anywhere from 4GB to 7GB. Though the hard drives are becoming cheaper these days, it's also important for owners of large DVD library to archive DVDs in a format that well balances the size and quality. In this case, you can mainly consider two formats: H.264 or H.265. But which to choose is based on your needs.

* H.264 supports up to 4K high-quality video with relatively small size. It's widely supported by modern mobile devices and other platforms. If you're ripping DVDs to a format for easier playback, H.264 is the way to go.
* H.265 saves 50% space than H.264 with the same high quality. It's the ideal format for 4K and 8K videos - best format for BD disc rip for quality/space reasons. But H.265 is less common than H.264 and requires more system power to encode, transcode and decode. (If you're interested, check H.264 vs H.265 for detailed differences)