All the arguments are valid. Last year i was building my house and was rally into solar, especially the microsolar water heater. Finally decided for steibel as the initial outlay was much less for 5 toilets, as i need hot water only for shower time, not the kitchen. Doing the maths, I wont use full hot water, just using the mixer to regulate the temperature of the shower and i dint spend much time there, maybe 2-3 minutes? All units are installed just above the ceiling and the copper piping is only 5 to 6 feet long.So far so good, instant hot water....maybe a 5 second lag.
Solar heaters need copper piping, thats costly if you wanna pipe the whole house and these are in wall pipes, you dont know when or where it can leak.
That my take, it really depends on what you require in your house.