using the equation q=m.c.delta T
where q is the amount of heat added, m is the mass of water, c is the specific heat capacity of water and delta T being the temperature change
q for 10ltr = 837kJ
q for 100ltr = 837kJ
so energy wise is the same energy, however how quickly you supply this energy will depend on the surface area of the heating surface, so I would say that 100 lts would be better
where q is the amount of heat added, m is the mass of water, c is the specific heat capacity of water and delta T being the temperature change
q for 10ltr = 837kJ
q for 100ltr = 837kJ
so energy wise is the same energy, however how quickly you supply this energy will depend on the surface area of the heating surface, so I would say that 100 lts would be better