Tankless is not hot on demand at the tap. If the tankless is replacing your tank, the water still needs to run through the pipes, so you still need to run out the cold water sitting in the pipes before the hot water comes through. There is a such thing as hot in demand, but then it is a small unit right at the point of the sink or shower that heats the water right before it runs out of the faucet.
Positives about tankless are lower gas bills and the water will run hot forever, you won’t run out if you take a long shower, or if ten people take ten showers in a row.
Negative is it usually costs more initially than a tank, it doesn’t hold any hot water, so if you lose power you won’t have a couple of days of warm water like a tank.
Gas tankless do use electricity. They have digital read outs, and maybe something else is electric in there controlling everything. If you lose power you have no hot water.
I have mixed feelings about the whole thing. Is there a big cost difference initially where you live?