I know for the 020, the main, practical difference is the EC version only supports 8 MB RAM. I imagine the same would be the case for the 030
The 68EC020 has a 24bit address bus, like the 68000. So it's 16mb minus roms & IO. On the A1200 you might have only been able to get 8MB fast ram, but you could probably squeeze some more in there.
The 68EC030 has a 32bit address bus. It's only difference is the lack of MMU.
EC just means it's cut down for embedded use.
