MakeMKV makes perfect copies that do NOT affect the quality of the video or audio in any way. All MakeMKV does is remove the encryption from the selected Titles and saves them as individual MKVs.
ISOs have a certain appeal because they are "perfect copies" of the optical disks in digital form. But ISOs also have ALL of the problems of optical discs:
* You have to sit through the forced trailers, forced warnings, intro sequences, etc.
* You have to use the menus of the DVD to get to playing back the movie.
* ISOs are STILL ENCRYPTED! So you must use some form of DVD decryption in order to watch your videos. With MC this is kind of hidden for DVDs. But for BluRays, you definitely need a third party on the fly decryption program like Red Fox (Any DVD).
* As you've noted ISOs must be mounted and unmounted, which is clunky.
With MKVs, you eliminated ALL of the above problems. No menus. No forced anything. No encryption. MC plays back MKVs natively without any "helper" applications. You just get to play your movie directly every time. MKV also handles multiple audio tracks and multiple subtitle tracks, which you can select directly, as opposed to using DVD menus to do so.
The only down side to MKVs is that your DVD/BD is no longer a single file with everything in it: Main feature, extras, etc. This can be a GOOD thing actually. If you aren't interested in all of the extras, you just don't rip them. If you don't want 5 different audio tracks with languages you will never listen to you don't rip them.
ISOs are an anachronism as far as I'm concerned. You can, of course, form your own opinion. Just know that MKVs, ripped with MakeMVK have 100% of the quality of the audio and video. There is no extra compression involved. It's the original format.
Brian.