Even the best tripod in the world is worthless if you use a cheap ballhead to secure the camera. I choose the Markins M-20 for a variety of reasons.
I looked at several other brands. I considered the Really Right Stuff BH-55, the Arca-Swiss Monoball-Z1, and the Kirk BH-1. On the Nikonians, most of the regulars liked the Markins M-20 and they have a great article comparing the most popular ballheads on the market at the time. You can read it here.
There is a great table that shows all of the weights, heights, load capacitys, and costs of the different ballheads. Markins was the obvious choice. It was the lightest by about a 1/2 pound. The Markins holds 88 lbs. of gear on the ballhead, which is second behind the Arca-Swiss by 2 pounds. I have no plans on putting more than 88 pounds of gear on my tripod. It is second lowest in height, only 5mm higher than the Really Right Stuff and it is the lowest priced ballhead by $15.
The performance of the Markins is great. Once you have set the basic tension for the ball so that it is adjusted to your specific camera weight, you tighten the small indented dial that is on the front of the main tension knob. After that is done, your tension can’t loosen up any more than than you set it at. That prevents your equipment from flopping around when it is at it’s loosest tension. You can tighten it down more, but not loosen it until you undo the dial.
It takes a little practice to be able to ge the tension just right to the point that the camera is easy to move but still stays in the position you leave it. When you find that sweet spot, the ballhead is a joy to use.
The camera is secured to the ballhead using a Arca-Swiss type of groove and rail system and there are two ways of securing it. One has a lever that tightens the clamp and the other a knob. I wanted the lever system, but now I’m glad that I got the knob because I feel that it is more secure than the lever method. I have read posts where the lever gets caught on something and opens by accident and the causes the camera to fall off.
There is also knob that tightens down the panning of the ball head. It is a great way to quickly move from side to side while the camera is still locked down.
Are there problems with the ballhead? Yes, but none that are really significant or cause me to want to replace it. The biggest problem is that when it is moist or misty outside, the ball can stick a little. A little WD-40 took care of the problem. Also, it took some time to figure out the best position for the knobs so they were easy to reach, find, and work with while in the heat of shooting. I found that having the clamping knob point to the rear of the camera is the best idea because if you put it under the lens, it can be difficult to get your fingers in and get a grip to loosen the knob. One time I had to use a pair of pliers to get the camera off of the tripod. The only other problem that I have encountered is that the panning knob can be hard to tighten once in a while.
Would I recommend the Markins M-20? Yes. Without reservation.