The debate about the best type of watering can is a healthy one. I think it makes sense to invest in a plastic watering can. The metal watering cans simply rust too much. You want to be able to find a watering can that is easy to lift as well. Currently, the evidence appears to show that the plastic cans would be more stable and consistent when in given hands. The flowers are not going to have as many chemicals on them with the plastic cans, in my opinion once the water is poured, at any speed.