The Makiwara is one of the least used, most misunderstood tools in martial arts training. Please review the following video; then we will discuss:

First, did you notice the shape of the makiwara?

This is not just a slab of lumber stuck into the ground (although that is what you commonly see in America). It is tapered, narrow, relatively thin and mounted to the wall in a spring-loaded base. The tapering shape allows the makiwara to flex with the force of a strike, giving but ultimately returning.

The spring-loaded base and the taper also makes the makiwara very lively; much more so than the ponderous swing of a heavy bag or the shudder of a free-standing water-filled bag. Pull your strike back, or the makiwara will give you a smart rap on the knuckles as a reminder!

Notice the string and weight hanging behind the makiwara? This is the "standard" if you will; strike the makiwara hard enough to move the weight (hopefully making it strike the wall behind) but also fast enough to get your hand out of the way before you get smacked.

This will lead you to develop speed and accuracy more than strength; but since Force = M^.V² you can quadruple your force for the same body mass by simply doubling your speed, with the added benefit of being able to strike again quickly (as demonstrated by Onaga Michiko sensei in the video; at the 2:25 mark).

Now do not get me wrong, mudslugging is powerful too but it relies entirely upon body mass and muscular strength. This is great so long as you are equal to or bigger than your opponent but you do not want to be smaller.

Second, the taper (which is NOT linear) provides "progressive resistance".

In other words the harder you hit the makiwara, the harder it will resist you. In a nutshell, the makiwara is good for all levels of power.

Heavy bags only offer a fixed resistance; therefore what one person strains to move another can move easily (and with little training value). You only need one makiwara; it will accomodate any size of student up to its breaking point.

In addition, the spring-loaded base and progressive resistance of the makiwara can be used to develop muscle resistance and the "immovable body" without having a partner to work with. Just push and hold. Do not let go. Keep holding..

Third, striking the makiwara does not hurt.

That is, so long as you use proper form. I am not saying it is impossible to damage oneself using makiwara, but really there is not much danger. On the other hand, sloppy form gets pretty quick feedback.

Striking a proper makiwara hurts less than striking your average heavy bag, and contrary to American belief it is not all about toughening up your hands.

Of course, if you have been pounding your hands into a 2 X 8 buried in a hole then I understand where you got that idea.

Rethink the makiwara.

P.S. -   those cheesy, cheap wall mounted stubby boards with a spring behind them are NOT makiwara. No matter what the manufacturer calls them.