Sorry but the question can not be answered! There are different virtualization technologies and each of them produces different service. Virtuozzo is totally different from VMWare for example. There are also Xen and etc. YOu can compare OpenVZ with its commercial and improved version Virtuozzo for example.
VPS hosting depends very much of web hosts approach to virtualization and to their service model. The other things technical support and customer care are very important and also can be considered.
I would suggest you to compare VPS hosting providers that offer services using the same virtualization solution. So the right questions would be - "Please suggest me who is the best Virtuozzo (VMWare) based VPS host?"
There is no outright "best" host. There is a best host for you and you will have to research that yourself, we can only guide you. Unfortunately, most of what you are going to get is recommendations based on limited experience, i.e. the host the person is currently on or has heard good things about.
Now, to help guide you, we would need to have an idea of your budget, resource needs, feature requirements, level of support, level of reliability etc.
So when we have a Virtuozzo as a requirement you can remove all quality VMWare, Xen and other VPS technology providers from the list and to compare hosts that offer Virtuozzo Containers based VPS only! That's why I said that we need to specify what exactly do you need!