The theory behind multi-tenant is that you should be able to reduce some of the memory footprint, on the premise that not all pluggables would be using all of their normal buffer cache at the same time.

Similarly, you'll have a drop in the number of background processes. Note - this doesn't reduce *load* because most background processes do nothing unless requested to, but each one does consume memory, so less of them gives you more memory to allocate elsewhere.

What is critical is that you make sure that all the stuff you currently will work nicely with multi-tenant. A common practice is to move/upgrade just *one* database to multitenant and then use that to identify any mods to scripts etc to work under multitenant.