I have used the products above and they are OK for a temporary fix that will get you through a season. The top up gas works well on a solid system that has just gradually lost pressure, but if you have enough of a leak to need the stop leak product, you will eventually need to get it fixed.
To do a refill job properly though you need to ensure the right amount of gas/liquid in the system. Pressure is a blunt way of checking this as it is greatly affected by temperature, and to a lesser extent by air pressure and humidity. That means without very specialist tools you will need to completely drain the system (vacuum pump and storage tank) and then add the right weight of coolant.