Why does Thunderbird sync all folders? While I prefer Thunderbird to Evolution, the out of the box setting is inverted for me -- Evolution never did that. In Thunderbird, I had to manually unclick many, many, many folders. In particular, the [gmail] folders, which hold the "all mail" directory, and so forth.
There's the Migration Assistant in the help menu which can set all of your folders to not synchronize. I think this was turned on to improve performance in general.