I have a VKB Gunfighter Mk.II with the complete Mk.III upgrade kit. I have the VKB MCG Pro, SCG Pro, and KG12 grips. I have also adapted my TM Warthog and F/A-18C grips to work with the Gunfighter. I swap grips periodically depending on which aircraft I am flying in DCS World.
The MCG Pro is the most capable stick with so many features that allow it to model the features of almost any aircraft stick grip, usually with buttons/hats/axes to spare. I like that its controls model the modern Russian grips, but it is a large grip and the controls can be difficult to reach/operate without shifting your hand up or down a little.
The SCG Pro doesn't have quite as many buttons/axes as the MCG Pro, principally because it has a single button on the right side instead of a pov hat. But it is sized / shaped / arranged to be more like US aircraft grips. Unless you need the brake lever axis or one more POV hat, the SCG Pro is a very good choice for comfort and functionality.
The TM F/A-18C grip has no axes and a few less buttons/triggers, but is otherwise as comfortable and effective as the SCG Pro. Because it is an accurate shape/arrangement for the F-15C, F/A-18C, and AV-8B as well as being reasonably sized/shaped to substitute for the B-8 grip common to so many US aircraft it is my go-to grip for flying US aircraft. The form / function of the SCG Pro vs the F/A-18C grip is so close, that it is a matter of personal preference, and I prefer the look and feel of the F/A-18C for many aircraft.
The KG12 is cool for flying Luftwaffe, but it was not designed very well compared to the later VKB grips. The POV had doesn't have a center-press function. Unlike the MCG Pro, there is no means for sims to know the position of the flip-down trigger. But it is cool to have the grip feel like what you see in VR, so it was worth it to me unless a better KG12 grip becomes available.
The TM Warthog grip is the one I use the least. It is only accurate for the A-10C and F-16C. It is a good stand-in for the B-8 grip in terms of buttons/trigger/trim hat, but unlike the real B-8 and the TM F/A-18C grip, I find its angular, squared off grip shape is the least comfortable. I know a lot of people like the feel of the cold metal, but I prefer the "warmth" of the plastic grips, which coincides with the material and feel of real grips.
So if you are going for pure capability and flexibility, the MCG Pro is the way to go. For a balance between functionality, comfort, arrangement, etc., the SCG Pro is probably a better choice.