The top knife in the picture above is about 3 mm thick at the spine, and about 1 mm thick at the mid-point between edge and spine. It is like a straight razor for shallow slicing tasks, but if you are cutting through something thicker than the width of the blade, the drag increases greatly. The thick spine tends to wedge on deep cuts. Forget any thought of twisting motions when cutting, you'll break a large piece right out of the blade. In spite of being a fairly inexpensive knife, it is the sharpest one I own.
The bottom blade is full flat grind, better steel, not quite as sharp, and sees a lot more use. The flat grind allows it to make deeper slices with little increase in effort, with much less tendency to wedge in the cut. The blade is thicker at mid-point and slightly thinner at the spine than the top blade. It is also the most expensive knife in the picture. As has been mentioned, full flat grinds require more grinding, so the cost of manufacturing increases.
The hollow saber grind , like the full hollow grind, is great for shallow slicing, but tends to wedge even more quickly. It is very sharp, and works well on thin materials. The saber grind relieves most of my worries about twisting motions when cutting, as there is much less leverage due to the smaller distance from the edge to the full thickness portion of the blade.
The flat saber grind is, at least for me, the workhorse/beater grind of the bunch. It requires more force to slice since the angle of the grind is wider, but the flat grind means the material is being wedged apart at a constant rate, where a hollow grind has an accelerating rate (the deeper the cut, the wider the angle the material is pushed apart).
Overall, I prefer the full flat grind as I feel it is the best compromise of strength and slicing ability, but it is not unusual to find me carrying a number of knives with different blade shapes and grinds, so that I can pick the best combination for the task at hand rather than compromising.
The only markings are: