Board Thread:Questions and Answers/@comment-148.109.1.11-20131219190545/@comment-32500188-20131224140713

Obviously, no matter who you ask, difficulty level of a voice bank varies per person, and to some extent, per generation of VOCALOID.

To add on to what everyone else advised (and to focus in on Angel's second point of advice), you might also want to look up or ask about any common issues with voicebanks you have a particular interest in, as well as if there are workarounds for them that you feel are reasonable to learn. There's no perfect voicebank, seeing as every one of them has their quirks or even glitches, so knowing exactly how much work would have to be put into a VB would also help you determine if its a good bank for you to start learning with.