>>2861380While not as flexible, bone morphs bloat your model's filesize less (which starts to matter when you constantly tweak it and accumulate gigabytes' worth of backups with low free disk space; not sure if they use less processing power in destination software). They are rare, of course, since people don't normally do advanced face rigging (and they also don't work in Blender and probably other software folks use, like Metasequoia), but I think having at least the upper & lower lip bones along with a lower jaw bone like that of Ademar's Izumi is advantageous for both lewd and gag works.
See Karin Anon's models:
https://archived.moe/e/thread/2772778/#2772849.
>>2861384Beware that you'll have to recreate effects from scratch for Blender if you want to "steal their look" after watching someone's video. Blender cannot into HLSL. Secondly, if MMM is simply poorly optimized (MMD is just slightly better), Blender's rendering speed is a whole abyss behind, so be sure to take that into account if you wish to post something for a special occasion.