IIRC "Transa" is Sam's all-time favorite Brazilian album
but TBH I've never been a huge fan of Caetano's London era in general. I'm definitely in the minority though- "Transa" seems to generally be his most popular album and considered to be one of the best Brazilian albums of all time. Not a fan of the English lyrics but it's mostly just the aimless nature of the material, especially on side 2 (but maybe that's what most fans find appealing? the "loose" aspect of it?).
At any rate, when I'm in a Caetano mood, I go for the self titled albums from '68 and '69 (the latter is my favorite) though both "Joia" and "Bicho" are very good as well.