I've tried to build a few big projects using vbcc with CubicIDE and I could never get it to produce a reliable exe. After coding for a few years now for Amiga 68k the only ones I've used to do anything with are StormC V4 (gcc mode) and AmiDevCpp.
Vbcc is a lot better with the last version but is developing slowly. There are newer versions of the vbcc assembler vasm that can be compiled to fix some bugs and add more optimizations. Vasm has been actively developed and is a mature product for the 68k. I wish GCC used it and a great project would be to try and retrofit it to GCC as it's supposed to be compatible with GAS. Anyway, vbbc does need some development. It's become more GCC like and more stable but it's still slow to compile and buggy on higher optimization levels. It does generate pretty good code on the low optimization levels which is good.
i think porting software you can forget about anything else than gcc. if you roll off your own project you can tailor it for something else.
You hit the nail on the head. Most software uses GCC and is customized for GCC. Porting with anything else is more difficult.