The A330's hold more cargo, have a higher passenger capacity, have been refitted to the latest Qatar interior and, based on current reviews, the A330 seems to be more comfortable than the B787 as the Boeing is described as cramped and narrow compared to the A330.
Yes, there was a recent review by a passenger who found his A332 from MAN in economy far more comfortable than his onward B787 flight. The B787 has, however, had some good reviews (if on takes much notice of reviews on skytrax) for its J class, compared to the B777 for example.
Capacity-wise, I don't know about cargo so I accept what you say. Passenger capacity doesn't seem much different. The A332 (vs2) is shown as 260 (24/236) and the 787 as 254 (22/232) so there are a few more seats.
My comment was simply related to the 787 being much newer equipment, but I agree it doesn't automatically mean it's a better pax experience.