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Vce can be modeled as a constant voltage drop in series with a small resistor. You may be looking at a semi-log graph if you see an exponential-looking curve.
A problem with paralleling three IGBT modules, as opposed to two, is simple geometry. It's harder to keep one from being hotter and getting most of the current.
I didn't want my post above to get too long, or I would have added a list of IGBT advantages. Foremost is that they are tougher than MOSFETs. Running a 300V device at 200V gives you plenty of room for inductive spikes, and they are fine running hotter than MOSFETs.
Second, they are usually packaged more conveniently for DIY builds. They have hefty, convenient screw terminals, a Kelvin gate connection pair, and an isolated base for easy cooling.
And they encourage using only one or two devices -- it's easy to forget how expensive it is to mount a dozen MOSFETs. Spring clips, screws, washers are easy to count. Board area, extra wiring, bus bars, drilling, tapping, isolation film, etc. can easily add up to more than the device cost.
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