MitchieM has been using Vocaloid for years but it's worth noting that he has acess to the new voice synthesizer developed by Crypton ( which isn't out yet ) and he used that in his newer songs.
We only know for sure that he used the Vocal Drive plug-in (for scream texture) and the HS Booster (to stretch out certain words), we don't know if he actually got to use the updated Crypton voice banks. And even if he did get to use the new voices, the new upcoming Piapro is for both hobbyists and professionals.
Haeven, in case you don't know, Crypton is going to announce to price of an updated Piapro by the end of this year (all of the Cryptonloids Miku, Rin, Len, Luka, Kaito, and Meiko have updated voices). However, we only know the new software will go on sale some time January ~ June. Crypton created their own software and are breaking away from Vocaloid.
This thread kept track of the entire progress of the situation.
I personally don't know if it's worth muddying your question with this information. But if you care about having the latest technology, you might want to wait for the announcement.