Good starting point as you consider your move to vSphere 6: Top 5 Tips When Considering vCenter Architecture Design in vSphere 6.0.
Choosing which type of deployment to use is critical. Once you’ve started building the environment, the model will be difficult to change and configuration limits could impact the scalability of your environment.
This is super-important and is one of the first decisions to be made when upgrading. Don’t just click…click…Next without fully understanding the ramifications of your choice here. More details are in the link.