"It still has a good rendering engine and the best animation"
Always my top two concerns, could be why I wouldn't consider moving to 3DSM or Lightwave an upgrade. I hear your point about the complexity of the applications, are you teaching general 3D visualization? In terms of interface, I think Caligari has them all whipped, though you can't do all the things you can in the others. Clearly if you are interested in teaching an application for useage(ie an animation studio looking for a person trained in xx application) then you wouldn't want to use tS, but it does do quite nicely for teaching the basic principles of 3D visualization.
"Those cheap bastard that are in charge of the money come up with this idea of buying GF2 MX for running Softimage, which also one of their bright ideas, instead of a professional 3D card. I just want to know if ATI Radeon is a better choice."
I think you will find that the GF2MX does quite a bit better in relation to pro boards then you are thinking. The GF2MX is certified for SoftImage, the SGI NT based workstations are not. The only boards that I can think of, besides nVidia(everything since the TNT2 using nV reference drivers) that has been certified to SI are several 3DLabs offerings, one E&S board(Tornado IIRC properly) and the FireGL. ATi has never had a board certified, their OpenGL ICD is quite bad. BTW- You can mod the GF2MX to a QuadroMX the same as you can a GF2 to a Quadro2.
For Lightwave I would expect the Radeon to do quite nicely, the Mac market is still very important for LW, I think that they would take the time to make sure it will run properly on ATi boards.
3DSM has never been very picky about boards, at least nothing like Maya or SI, and the Radeon should do quite nicely there, though with heavy geometry loads the GF based boards are likely to be much faster.
For pricing- what kind of deal are you getting on 3DSM or Lightwave? Avid has a deal going on right now where you can get the latest SoftImage for ~$500 for educational purposes(students, schools and teachers). IME, Discreet has charged twice that for 3DSM educational licenses though I'm not sure what Newtek gets(never even looked).
"I just want to know if ATI Radeon is a better choice."
I would say no. Sorry if I went somewhat off topic, it gets boring arguing over which vid card can run what game 2FPS faster

