I think I know why the two lakes fished so differently.
The larger lake was more heavily fished by more pike anglers, and I think that the pike had been pressured on most deadbaits, with the exception of blueys, so where Colin and I were being different, and casting regularly we simply picked up on a group of fish a big quicker than other anglers, although eventually we had a blank or two as well.
The small lake is bowl shaped, with a ledge around it. We got our takes with the Mackeral deadbait landing on the edge of the ledge, basically perfectly positioned for the pike to pick up from underneath.
Sadly I can't remember the weather pressure during most of the trips, but it wasn't too cold, until the final trip on the smaller lake we managed when it was only just above freezing and with showers, and my mackeral was picked up by a 20+.