けど vs. が for “but” conjuction

Question

This question covers the difference between でも and けど for "but", the difference being that でも can be used at the beginning of a sentence. But けど and が are used in very much the same way, syntactically. What exactly is the difference between these two expressions?

Answer 1

今日はサッカーをして疲れたけど楽しかった。
今日はサッカーをして疲れたが楽しかった。

　

去年は遊びまくった。けど、成績は落ちなかった。
去年は遊びまくった。が、成績は落ちなかった。

　

ご飯食べるのはあとにしよう。おなかすいたけど。 
ご飯食べるのはあとにしよう。おなかすいたが。

By comparing these sentences, "けど" appears to be softer and more common in informal speaking. "が" delivers a sense that the speaker/writer is assertive, often used by a person in a higher position or in formal writing.

Answer 2

I think that が is disjunctive while けど is concessive. That is to say that が may connect two disjunctive (disconnected) parts, while けど not just connects the two but introduces the succeeding clause as a circumstance that might be expected to preclude the action of the main clause but does not.

I think the term "disjunctive" is a superset of "concessive". That is to say that "disjunctive" includes "consessive".