Wow, that is too bad. We have it on our VPS, gotten used to it and love it. No so good experience with WHM/cPanel in the past at another hoster.
So Plesk is gone for good I take it from KH .
WHM/cPanel was slooow. Service not so good of the old hoster. This was a few versions back. We really like the way we can go in and out of the accounts inside one panel in Plesk. Also plesk can handle multiple shared IPs. My understanding is that WHM/cPanel can only have 1 shared IP addy.
I know you guys can do it but now I have to tell clients / developers we are changing the interface and that is usually not received very well. The only way I would consider the switch is to slowly switch over (move sites slowly) and giving developers / clients a chance to adapt slowly. So I would open another VPS and move stuff slowly over to the new WHM/cPanel system. One of the issues here is how to handle the DNS (NSx, NSy, etc...). Can two VPS have the same / share DNS set up?
Your input appreciated.
Sure, cPanel fully supports clustered DNS.
Technically they could be wrangled together to all play together I think. Having cPanel already hosting DNS for not-yet-moved systems might cause some issues/conflicts when you go to actually create the account.
The best thing to do in a situation like this is to make the move all at once. We'll give you some ways to test sites and such before flipping DNS so you can do some verification.