All other factors kept constant size of engine translates to the fuel consumption so for vehicles of the same size (weight) fuel efficiency is higher on a 1000cc than a 1500cc. Putting the weight factor, other factors kept constant a heavy vehicle (belta) on a 1000cc engine performs poorly on both fuel efficiency and power than a light vehicle (vitz) on a 1500cc. Generally the belta 1000cc drags a lot and you can feel it struggle a lot when carrying 4passengers on a hill compared to its vitz 1000cc counterpart.
So if I were you I would choose from either vitz 1000cc/1500cc or belta 1500cc. Again doing a lot of city travels is a good factor to consider but remember once in a while you may need to go out of the city and during this one time you will dread your 1000cc and only one time encounter is good enough to make you wanna leave your car on the roadside and walk.
If it was me buying....I would go for belta 1500cc. Enough and more secure boot space, bigger and considerable power.
