well I mean for one, not every cvvc bank follows the oto that matches the autocvvc converter. And when it comes to fast songs, you have to deal with really tiny notes
That can be rectified by the creator of a given bank making a CVVC dictionary to load in autocvvc (easy to accomplish once you get a grasp of how it's set up). For faster songs, 9 times out of 10, you can get away with using CVVC banks in CV mode (if the oto is well done, then you don't even need to convert - or even use presamp - beyond adding a dash to notes after a rest and vv transitions).
To avoid double posting: I prefer CVVC as it's faster to get done, can be used for virtually any language, and allows for more control over results.
While VCV certainly isn't bad, it's only really useful for Japanese and other languages that don't require phonemic complexity. It also can be more problematic if you...
- are a newb who hasn't changed locale (or aren't a newb but just refuse to/aren't able to) and want to DL banks. More often than not, VCV banks are encoded in hiragana which will become mojibake. It's rare that people provide a romaji encoded bank these days; even rarer if they provide a romaji oto.
- are a Mac user trying to make your banks available for PC users and use the wrong archiver (dakuten and handakuten get read as gibberish to Windows and UTAU PC treats these glitched wav samples as if they don't exist)
- are a Mac user trying to load certain banks and they simply... crash for no apparent reason in UTAU-Synth for one person and work fine for another (I'm not saying CV and CVVC banks don't have this problem; they probably do, [IDK; I'm not a Mac user] but there's been no reports that I'm aware of in terms of UTAU-Synth or PC UTAU under WINE. I pretty much only see threads pertaining to this issue in regards to VCV banks).
- have limited HDD space (looking at you Gahata Meiji, Koharune Ami, etc. etc. and all other VCV banks that go beyond 750mbs).