Quite possibly the most frequently debated topic in bowhunting is which broadhead is, "the best."  While "the best" is strictly a matter of opinion, I'll try to clarify the Pro's and Con's of each, Fixed Blade and Mechancial broadheads.  Keep in mind that any broadhead will do what it's intended if it is placed in the proper location, select your equipment for the worst case scenario not for one that is perfect.

Fixed Blade Broadheads:

Dating back to the days that Native Americans roamed the plains, the fixed blade broadhead was in existence.  In the last 250 years, arrowheads or broadheads have advanced in the same manner as any other product in the world.  Today, we as bowhunters have literally hundreds of choices when it comes to selecting a fixed blade broadhead.  A fixed blade head is exactly as the name implies in that the blades are fixed as they don't move throughout the shot at any point. Let's look at the positives and negatives of these heads...

Pro's:
Fixed blade heads are extremely simple.  There are no moving parts, rubber bands, or other devices required for them to work properly.  They have a reputation for being the tough and rugged type head that holds up the best to the abuse of an everyday hunting head.  The majority of fixed blade heads have removable/replaceable blades rendering a head reusable if a blade becomes damaged.  This is one of my favorite features as $10 for a pack of replacement blades is easier to swallow than $30 to replace three broadheads.  Fixed blade broadheads are very suitable for low poundage setups that don't produce the high amounts of Kinetic Energy (KE) required for opening mechanical style heads.  Penetration is probably the largest advantage that a bowhunter will gain by selecting a fixed blade head.  They eat up zero KE in order to perform, allowing all the energy of the arrow to be transferred into the target.

Con's:
There are very few negatives to a fixed blade broadhead, the two main complaints being their flight pattern and the smaller cutting diameter in which they are available.  Many bowhunters experience that the flight of a fixed blade head is can very different than that of a field point.  Speaking from experience, this can be an extremely frustrating issue.  Thankfully 99.9% of the time, this issue can be corrected with a little bit of bow/arrow tuning.  The final complaint (that I'm aware of) is that fixed blade heads are available in much smaller cutting diameters than a mechanical head.  I'm not able to think of a fixed blade head that offers more than a 1-1/4" cutting diameter.

From Left: Slick Trick GrizzTrick, Slick Trick Magnum, Crimson Talon, Crimson Talon Hyperspeed, Muzzy 3-Blad, Eastman Terminator

Mechanical (Expandable) Broadheads:

Mechanical heads are also referred to as "expandables" as their cutting diameter expands as it enters a target.  Mechanicals are overwhelmingly the choice of broadhead style for turkey and small game hunters and many deer hunters use them as well.  With heads like the Rage slip cam, their popularity has skyrocketed in the last few years.  Let's look deeper at mech heads...

Pro's:
Upon screwing these heads in place of your field points, nine times out of ten they'll be close enough that you can't tell the difference.  They offer the combination of tip weights, blade numbers and sizes that fixed heads offer along with the addition of a significantly larger cutting diameter.  Due to the generally larger cutting diameter these heads are capable of creating an incredible amount of tissue damage, I believe there are mechanical heads that advertise a 3" cutting diameter!  With a bow producing adequate KE mechanical heads are an inviting prospect to tip your arrows.  

Con's:
As we've heard so many times, "every rose has it's thorn" the same is true with mechanical heads.  The majority of mech heads require a rubber band, an O-ring, or a string of some sort to hold the blades in place until they're expected to deploy.  If there happens to be an issue with the rubber band the heads can be very noisy or worse the blades can open in flight causing nightmares for a hunter.  It's always possible that these blades open too early or too late, an issue that is completely eliminated with a fixed head.  Penetration can suffer because of the KE that is used to open the blades (more significantly so with blades that open from front to back).  The blades of these heads are (as a whole) less durable because they are thinner and have to move to work properly, making them weaker than that of a fixed blade.

My main complaint with mechanical heads is that they are used to cover up tuning issues, unbeknownst to most people that use them.  Generally people switch from a fixed blade head to a mechanical because it "flies like their field points."  As discussed previously this issue can be corrected most of the time by simple tuning.  This means that the arrow isn't flying "true" to begin with and is then tipped with a head that often times hurts penetration, thus compounding the effects of a poor performing arrow.

A few of the most popular mechanical heads would inlcude: Rage, N.A.P. Spitfire, Vortex, Rocky Mountain, Wasp and Aftershock.