Supply water temp can make a huge difference in your satisfaction with the unit. It all depends on your usage rate of flow. The units essentially make the heat in a very short path and they can only raise the temperature a certain amount. So, if it is designed for say 70-degrees at your desired flow rate, that would likely be fine in the summer when the incoming water is 50-degrees (50+70=120 output). But, where I live, I've measured winter incoming water temperatures at 32-33. So, 32+70=102= a cool shower. If nothing else, you'd have to adjust the antiscald shower valve to allow more hot water in during the winter and lower it in the summer since most cannot provide full hot when adjusted properly for the summer water temps.
WIth the additional cost to purchase and the annual maintenance generally required (depends somewhat on how hard your water is), a good gas-fired unit is often a better buy. And, while a tank may last longer with some maintenance, most people don't do that, and they work until they die. You could probably buy 2-3 gas units before you came out even, and thats if you do the maintenance yourself. The better gas units don't really have all that much standby losses (the electric are better on standby losses since they don't have a flue up the middle). And, if the WH has an automatic damper, that loss is minimized even more. The biggest hassle with installing a gas unit where there hasn't been one before may be routing the flue and chimney. The tankless parts, if you ever needed some, are less common, and if it dies, you may need to wait. That means you're out of hot water for maybe a week or two by the time you get it diagnosed, the part ordered, and then they come back to replace it. A traditional tank unit, you can often get one replaced the same day, and parts are generally easier to find.
Any tankless will have a lower temperature output as either the incoming water gets colder or you try to use more water (within limits - some modulate, but if it requires full-bore burner, it can only output so much heat). If you are trying to get a minimum flow (warm water), it may not be enough to trigger the burner at all on a tankless. A traditional tank type gets you full temp until it gets emptied, regardless of the flow or incoming water temps.