User account invisible on start up
It's hard to know what slow means. If you have FileVault enabled - only accounts that are cleared to unlock e drive show up after the boot to the pre-start screen. 

Once one of those users authenticates, the volume gets unlocked and then the OS boots. If you don't expect this layer and seeing the OS boot after user credentials are presented, that might explain everything. Without a stopwatch to time what is slow, it's hard to tell more what you are seeing. 

Since all new hardware gets AppleCare for questions like this, I would get their help narrowing down your variables and perhaps ask a follow on question with some specifics if needed.