@[deleted] DeoVR is a very useful app, but it is lacking in several functions that are essential for foreigners like myself.
DeoVR does not support multi-lingual tracts in MKV files. This option may seem like an unnecessary extravagance, but I'd bet the JAV studios on this site could benefit from the versatility of MKV submissions. MKV can include multiple language tracts as well as different subtitles. Of course, there are very few options for some languages and this type of content. However, it is possible to create one language file and then process it in a dozen different languages, for a variety of viewing audiences.
DeoVR cannot be a standard player because it has difficulties with non-standard film dimensions and 3D content. Sometimes while encoding film (like for back-up purposes from a personal collection) one accidentally encodes the black lines around 16:9 . SkyBox provides a number of options for non-standard dimensions. Of course, this probably isn't a major concern for SLR. Yet it is a requirement for a good standard player.
As @catflap says, offline viewing is essential for us poor foreigners. Internet Access at a fast speed certainly is not dependable. Often everyone from the neighborhood will be online at the same time of day, so I try to download stuff, if I can, and then upload it prior to viewing.
So SkyBox is my regular viewing software (for 3D films, cinematic releases, classics mainly) and DeoVR for VR180.