It really depends on the situation. One of the biggest issues is incoming wintertime water temperatures and how hard the water is. Next biggest thing is what volume of water do you need and for how long and often, including how fast.
Filling a large soaking tub fast is not one of the things a typical tankless can do. But, if you gang multiple ones, the sky's the limits, but at a cost in both infrastructure to make it work and up-front costs to make it happen. That might be an advantage in say a spa or bathhouse.
To me, the delay in producing water, the inability to do it at a low volume where you might want warm water, the infrastructure upgrades that may be needed (gas line sizing, meter, etc.) and the need for what is probably annual maintenance to clean up the heat exchanger would limit the situations where it is useful.
Both electric and indirect WH can be made with some pretty good insulation. My indirect let me take a hot shower for three days in early spring when my boiler died on late Friday. I did not want to pay for it to be dealt with over the weekend.
Last bit, finding someone who understands and can service the thing AND has parts, when the time comes, can vary radically depending on where you live.