I personally like Storm C 4 with its nice integrated front end and compiles clean C programs. Although I cannot get it to compile WB programs that can be launched from Workbench properly (Itried including wbstartup.h but doesn`t seem to make a difference). You run the program but nothing happens, I have to run them from a Project icon.
SAS/C 6.58 has been good but lacks any decent IDE. There is a lot of legacy stuff and C++ support is v.poor.
GCC is ok but can be a nightmare to use for beginners. Gccopts doesn`t have enough options included. There is no option for including maths (-lm) when running make, I have to do it via gcc compiler command line. A pain. BTW, where can I find a pre-compiled version of GCC 3.x for 68k (only 2.95 is on Aminet)?