Advice Required: Tankless with Storage tank /with winter Hydronic use

[CanadianEh]

Here is what I have going on, and wondering if someone can help me solve the problem..

Quick details: I live in Canada so the cold ground water temp can be an issue in the winter.

I had a Bradford white 75 gallon water tank that just gave up. This tank was used for my main home hot water, as well as sent hot water to a heat exchanger to run the hydronic system in my basement slab. I feel this system was inefficient. Unfortunately I do not have the capital to put in a boiler system.

So here are my options.

- Replace the tank with the exact same thing and set it up as it was.

- Switch to something else, which should gain efficiency.

I have had a few plumbers by to discuss.. both seemed to just say replace the tank as is. They didn't have any reasons as to why, just the easiest solution.

One I spoke to on the on the phone mentioned He would consider doing an On demand tankless system with a small storage tank. This got me to thinking this maybe the best solution for my situation.

I am curious as to other plumbers thoughts on this and how you see it working?
would it be more efficient?

Any advice is appreciated.