Supermodel is C++. The CPU cores are technically still in C but in practice, this distinction between C++ and C is irrelevant. I'm surprised this debate is still active over here in the year 2011 but I guess none of us would be here if we didn't enjoy nostalgia
As RB says, it's all about the algorithms. The main reason Supermodel is slow, for example, is the graphics engine. There's a lot that can be done to optimize the rendering. The single biggest performance killer is the bilinear interpolation done by hand in the shaders. It's madness to go about it this way, since just about every GPU since 1997 could do this in hardware, but I need to get the Real3D to give up a few more of its secrets before I write a smarter model and texture caching/preprocessing system.