I find 'take out the trash' so much less hsrsher than 'you will take out the trash'. The first statement permits the response 'no'. It is clearly an order, with room for agency on the other side. The second statement doesn't permit a response. To disagree you have to say 'you are wrong'. The statement leaves no room for free will. It assumes the authority of the command to be overwhelming. Or perhaps it is a threat.…
“You will speak when you are spoken to” -> Very aggressive “You will be joining the oncall rotation” -> Quite friendly
The second one reads as a news report: like I, the reader of the oncall rotation, am sharing the news that your name has come up. (If I was the sole controller of the oncall rotation it might come across a bit differently, as an actual command).
I like the contrast of these two!