Win8 Hybrid Shutdown/Fast Startup vs IRST?

I'm in search of the "fast boot" holy grail on:

- Gigabyte H77M-UD3H motherboard
- i3-3225 processor
- 12GB RAM
- two SSDs: 120GB Intel 520 & 64GB Kingston SNV425S2
- a 1TB HDD
- Windows 8 Pro x64
(I hope that's all the relevant factors!)

Although it was a bear to install, I persevered and IRST is now installed and enabled. There is a 13GB partition for it at the end of the 64GB SSD.

Hibernation was disabled so Fast Startup wasn't enabled. Fixed that and created a desktop shortcut for "C:\Windows\System32\shutdown.exe /s /hybrid /t 00"

Startup does seem faster, but I'm not sure which is responsible. Are they complementary, mutually exclusive, or peacefully co-existent?

If I disable IRST and use only Hybrid Shutdown/Fast Startup and compare it to full shutdown (using /f switch) with IRST enabled, they seem the same as with both enabled. Disable IRST and use a full shutdown, and it does seem slower to boot.

So, what's the difference between Win8 Hybrid Shutdown/Fast Startup and Intel Rapid Start Technology?

This Microsoft blog page pretty well explains Hybrid Shutdown/Fast Startup, but I can't seem to find any explanation of what IRST really does.

The only "objective" test I did was enable BootRacer. However, when Hybrid Shutdown/Fast Startup is enabled BootRacer doesn't record the time to logon nor save any times in History to compare.