This debate comes down to initial installation cost in most case’s.  Let’s face it when the cost of replacing a 10 to 20 year old water heater is going to be in some case’s twice as much, the decision is swift.   “I’ll stay with my regular water heater that for the most I forgot what it looked like till it leaked”.  As far as efficiency goes hands down the tankless option wins.   It only heats the water as it is in demand.  But how much does it save you on a daily basis?   Is it enough to warrant the investment?   You also have maintenance to perform semi annually or annually depending on the quality of your water.   A water softener is highly recommended with a tankless system.   Granted I like soft water and feel everyone should have one, but selling a tankless system is hard enough.  Tell someone they also should spend a bit more coin on a softener is a bit of a task.   In my opinion new construction homes should go with a tankless.  That is if they are gas or propane,  electric systems should stay tank, but should be hybrid type.