Keeping in mind your 16km daily commute in heavy traffic and the occasional 800km highway run, we would recommend going for the Kia Sonet HTX DCT as it has the smoother gearbox of the two. It also feels more premium inside out, and except for rear space, which is just about enough, the Sonet does feel like a more rounded product than the Tata Nexon Creative DCA.
That said, if you are looking for more space, there are two other cars with the same engine and gearbox combo as the Sonet and those are the Kia Syros and the new Hyundai Venue. Both these cars are newer than the Sonet, which is due to be replaced in about a year with a brand new model. Both these cars are more spacious and have more features too.