First what are you using as a fuel source. If your using natural gas or propane I would not go with a tankless coil. If you are using heating oil as a fuel source you have a tankless coil as a option. With a tankless coil you will get around 3 to 6 gallons a min. Your shower uses 2.5 gallon per minute. A tankless is a unlimited supply of water if you have a large family or use a lot of hot water a tankless will never run out of hot water. Both tankless and tank can develop lime problems. Water quality has everything to do with Water heater longevity.
Most important thought is fuel source. Gas just no have enought BTU's If you have gas check out gas insta hots( rinni, bosch, or aquastar) this is avery good way to make hot water.