No reason not to switch around. With Red and Green you get more Healthy Extras (2 A's and 2 B's) but have to use syns/HEX's for meat (on Green) or grains, pulses, potatoes etc (on Red).
I don't get on with EE cos I like my HEX's and don't eat much meat at all, so I stick to Green and use meat as HEX unless I'm making something with a lot of meat in as a one-off, in which case I switch to Red and use HEX's for the rice/potatoes/lentils/whatever I'm having with it.
I guess EE is best if you like to have a lot of both meat AND carbohydrate-rich stuff like potatoes, rice, lentils. I'd say generally if you eat mostly meat Red is easier, if you hardly eat meat Green is easier. But I just adapt it depending on what I'm planning to eat on any particular day.