Transit or visitor when travelling through Newark en-route to Canada - with a stop in US on return journey

I shall be travelling to the US and Canada this month, and have a query about US customs. We are British citizens both with ESTAs, so are eligible for VWP, this question is not about visa requirements. We are travelling to Canada via Newark airport with an overnight stopover on the outward leg of the journey. This stopover is at one of the airport hotels. On our return journey, we fly back to Newark and the are staying in New York City for a few days. When entering the US on our outward leg do we need to tick the box for transit or visitor? And, on our return journey will we need to pass US customs again as if it were an entirely new visit? Or, if we enter the first time as a visitor will it be counted as a single trip?