There are two choices you have for your home:
Once you make a choice between those, you then have other choices to make:
The most important choice is whether to install insulated ceiling openings.
See the INSULATED SYSTEMS That MEET IECM2012 SPECS
Next, how many speeds are best for your needs?
SPEEDS – 1, 2, 3, 4, 6, OR INFINITE?
Air flow – you need to decide how many CFM you want. The more the better.
CFM – HOW MUCH DO YOU NEED?
Attic ventilation – what goes up must go out
VENTS IN YOUR ATTIC – HOW MANY DO YOU NEED?
Efficiency – This varies greatly between suppliers. Do you want to pay more for better efficiency?
EFFICIENCY – WHAT DOES IT GET YOU?
Here are some more details:
SOUND LEVEL – WHAT ARE SONES AND dBA?
CALIFORNIA ENERGY COMMISSION LISTING – WHAT DOES IT MEAN?
SILVER FOIL ATTIC RADIANT BARRIER – HOW GOOD IS IT?
INSTALLATION – CAN YOU DO IT YOURSELF?
ACCESS TO YOUR ATTIC – YOU NEED TO KNOW EXACTLY
JOIST SPACING – DO YOU KNOW YOURS?