which is More Efficient?Gas vs.Electric Water Heaters

Well, it depends on your local utility costs. Gas water heaters are usually cheaper to operate than electric, but they also cost more upfront than an electric. However, based on energy savings, gas heaters generally make up the difference in price in about one year. Cost: $300 to $600 for gas and $250 to $500 for electric. Read more https://iwaterpurification.com/best-electric-tankless-water-heater-reviews/

The energy cycle in both needs to be looked at. Each step in the cycle there is a efficiency loss, so the more steps the more inefficient thus adds cost.

Gas (say 4 steps)
Drill well, pump gas, distribute to costumer, burn at costumers site.

Electric (made from NG) (say 10 steps)
Drill well, pump gas, distribute to power plant, burn at power plant, create steam, turn turbine, transmit on high voltage lines, convert to medium voltage, convert to resident voltage.

In electric you have tons of loss in transmission that is hard to account for but you are 100% efficient at converting it to heat in your hot water heater. Gas is opposite, distribution doesn't have much losses but is only ~90% efficient converting to heat at your house.

So the "efficiency" of Natural Gas is going to be magnitudes better then electric because of all the conversions and transmission.

An electric water heater with the heater element resistor power-optimized for a string of PV panels directly hooked up to it is about as efficient as it gets, but I doubt that's what you're really asking about.

A heat pump water heater can put 2 to 4 times as much heat into the water as the electricity it uses by taking it out of the air, which in simple terms would be 200-300% efficiency. You're probably not asking about that either.

So what do you REALLY want to know- thermodynamic efficiency, net operating cost, lifecycle cost, temperature recovery time, or... ???