Are markets that are good for trend good just because they have also gone up a lot, or because carry, or...

I have a friend, ex-colleague and TTU co-host who runs a fixed income focused CTA. We have regular coffees (he pays, so his fund is doing ok) and one of our favourite topics for arguing debating making polite conversation about is why fixed income is so much better for trend than anything else. He's biased, but then arguably so am I; I started my career trading rates options, and we both managed…