It depends which variant you are buying. For such a limited usage, out of three choices you have made, a Swift LXi will do it’s job and you will be able to save 40 to 50 thousand rupees (fuel + maintenance bill for 3-4 years!?) over i20 Magna.or Swift VXi.
The Swift and Dzire are essentially the same, except that you get about 100 odd litres more of luggage space with the Dzire. Do you really need that space? The i20 on the other hand has slightly better interior space, but its maintenance costs are slightly higher as well.
Boot space on the Swift is really very limited. You should consider other options if this is going to be the only car in your garage.
i20 all the way better than swift and dzire