I have now tried Zwift and I'm not really impressed. I don't think the drafting experience was that much better than BKool's, and certainly nothing like the real world. The speed is perhaps a bit more realistic.
The biggest difference to me is that the climbs are not as tough, and when sprinting the speed only gains slowly, as to accommodate the missing initial BKool resistance.
The only nice feature which Bkool hasn't got is the peak watts popping up after sprints

.
Well, now that I have my ride on Zwift, I can't seem to do much analyzing. When I download the fit file, it only contains speed data

(I didn't have the Strava connect enabled).