I know that Microsoft suggests that you leave 1GB of memory for the parent partition on a Hyper-V server. Does VMware have a similar suggestion?
Memory overhead is going to hinge on a lot of things. Luckily, VMWare has a nice little table to let you know what to expect:
In practice, based on the few that I run in production, the ESXi core uses around 200 or so mb. Personally, I try to keep around a gig free of non-reserved ram per server (200 reserved for ESXi, 256 mb for Linux guests, 512 to 1024 mb for Windows guests depending on version and services)...