As many of you may have heard last week, we were mistaken in our assertion that machine-specific variations in sim performance are negligible. There is a difference, and we're working on a way to manage the differences fairly.
Our current thinking is that we are going to map simulators to classes of CPU's so that you never get a machine slower than the original machine deployed when the land was first put online. What this means is that the older sims will indeed have servers with a slower CPU. These servers will be replaced by new machines when they reach the end of their useful life, although we don't know yet what the schedule will be.
Over the next several weeks we'll be posting a complete list of sims, and what class of server they're mapped to. At that point you can decide if you want to move to a different sim or wait until the server is naturally upgraded through attrition.