May or may not explain your experience, but OSX caches a bunch of stuff on startup, and if nothing has changed the next time you start up, it just uses that cache and can start up MUCH faster.
Because of this, if it's just a "regular" boot when you haven't installed anything or manually cleaned out caches, it's usually very quick. If you are restarting from a software update, then it needs to do a "full" boot, and takes maybe 20 or 30 seconds longer.
In my experience the part that this affects most is the part where you see the progress bar; when it's a cached boot, the progress bar is onscreen for about 3 seconds. When not, maybe 20 seconds.
I believe if it was a forced reboot the system will also do a disk check at restart, which happens while the spinner is onscreen. Not positive about this, but I seem to notice it taking a lot longer after a panic.
My 1st-gen 17" takes maybe 30 seconds to boot, for reference.
Does the MacOS do a RAM test these days? That'd also affect boot times if you have more RAM...
