“which” command difference

What is the difference between (unix-system “which [name]) and which [name] commands.

For example when I use the (unix-system “which visual_elite) command I get the following result:

/home/vhdl/edatools/mentor/visualelite/VisualElite-4.2.1/Linux2.4/bin/visual_elite

When I do the same on the command line using which visual_elite I get

enidl-atlas-schur <76> # which visual_elite visual_elite is /home/vhdl/edatools/mentor/visualelite/VisualElite-4.2.1/visual_elite

Why do I have this difference?

Thanks,
Mihaela

Both commands seem to produce the same result.
Maybe one is executed from a certain directory and the other is an "alias" script on a different directory and the one executed will depend on the location of that directory in the PATH variable.