For most people, a tank-type WH is a no maintenance item...while you can sometimes extend the life by treating it better, they tend to just work until they don't, and then you usually replace it. This is NOT true with a tankless system which costs more to install and will have problems if you do not do regular maintenance on them. Overall, they can last longer than a tank-type, but that isn't always a given. The parts (say a control board) are not particularly cheap nor is a heat exchanger. You can find someone to replace a tank-type WH pretty much anywhere, anytime (you'll obviously pay more off normal working hours, but they can do it). Finding someone that understands, has the parts, and can fix a tankless system is not a given. You may be in an area where they are well supported, but a typical plumber doesn't have the parts for fixing one.
On a tank-type system, the larger the tank, the lower the surface area, so there's the potential of lower standby losses. IOW, two smaller tanks will have more of a standby loss than one equivalent larger tank, especially on a gas-fired one.
Putting in numerous tankless systems will probably mean greatly expanding your gas service. Even though your average use may not be huge, you'd have a HUGE peak demand. SOme utilities base your customer charge on the demand level, and that could go up significantly. A typical tankless system runs around 200Kbtu, and the gas line must be able to support it or the things don't work right at all. This could be a huge extra cost to expand the gas supply, maybe back to the road, and likely at least the meter and internal piping.
Teenagers will tend to take long, hot showers unless you enforce the issue. That can be tough with a tank. Personally, I'm in that category! Plus, I have a 6' tub that I use regularly which helps my back.
If you have the vertical drop, a hot water recovery system can make a tank function as a much larger one when taking showers (doesn't work with tubs - there must be hot water going down the drain, and a tub doesn't have that until you're finished).
When the hot water source is a long ways from the point(s) of use, during the remodel, you might want to install a hot water circulation return line and plan for a pump. You should also insulate all of the lines. Without one, in a large house, the furthest point of use could take minutes to get hot water the first time of the day or after a gap in hot water use. Keep in mind that even before you get to use it in that case, you may have pushed 3-4 or more gallons into the WH while it's purging the lines, decreasing the amount of hot you ultimately could use.
