^ If you have a bluray drive and burner, you can re-create the disc yourself. If you don't but you have the right software, you can view the DVD menu which is kinda nice I suppose. Possibly even access the bonus vids (if any) if they weren't also ripped. However, the video quality would be pretty much the same if the ripper did a decent job (in other words, if its not ripped by those idiots over at youiv) but that's usually the case here as folk here know what they're doing.
My advice would be for you to download one other non-bluray DVDISO to try it out as that's less bandwidth intensive. Than you can see what its like. Than you decide for yourself.
Note that some makers do a better job than others. Some of them are lazy/cheap? and the DVD menu is plainly done. Just a simple still pic, chapter markers are just plain numbers, no bonuses, etc. However, TakeShobo (TSDV/TSBS) generally do a decent job of it. Their menus usually are animated, chapters are shown as short preview clips, there is usually an idol profile segment, and there would be bonus videos, photo shoots, and clips of other releases too.
Edit: OK, to further save you the trouble of downloading, I'm including some screencaps of what its like. But please note that its not of this video as I didn't grab it myself. This is from TSDV-41642 featuring Narumi Okawa. Its also a TakeShobo title, so it should roughly be the same.
This is the menu. The background is an animated movie of Narumi running on the beach (ch3 of the same DVD).
Chapter list for this is just a still snapshot however. Some have short animated preview clips.
A profile page.
A slideshow album.
And you get some sample clips of other videos from the same maker. This one is of Hiromi Yamakawa. I don't think of of her vids have ever been uploaded anywhere before.
Its fun to have. But is it worth the additional bandwidth and hard drive space? I'll leave that for you to decide. Personally, I only grab the ISOs for idols that I really like.