The K&C, JJD, and FL figures are all fairly old; the painting standards for all three companies have since increased dramatically. That said, here are my honest notes (setting aside my personal collecting preferences and acquaintances with manufacturers):
K&C: the painting is crisp and there is some weathering. The detail on the drum is around equal to the VID figure. The face is much bolder than the VID, FL, and KP figures, but has around the same level of detail. The sculpting is a bit bulky, but the gear looks complete and each piece is clearly demarcated. The reliefs on the brass are minimal or non-existent.
VID: The painting is rather pale and lacks much weathering, but the detail is there (see my comment on the K&C drum). The face is well-sculpted, but the painting is a but rough. The figure is much less bulky than the K&C one, but some of the gear lacks certain details. The brass has good relief.
FL: the shading and colors are excellent, but the face is a bit sloppy (it just looks a bit odd.) The details on the brass, shako, and drum are all quite fine and well-highlighted. The body shape is a bit strange.
JJD: the weathering is nice but the blocky painting style is not my favorite. The face is a bit rough, but the dramatic pose sets it apart from the others. The detail is all there, but the bulky nature takes away from this.
KP: This looks to be the best proportioned figure, and the painting is kind of average, which I mean in a good way; it isn't too pale or too bright. The level of sculpting detail is approximately equal to the VID figure, but the face is better.