Of the two cars you've suggested, and given your requirements, we would recommend the new Kia Seltos. 

For one, you'll find it a more natural upgrade from your Hyundai Venue 1.0 Turbo DCT, as both cars come from the same Hyundai Group family and use related hardware. That being said, the Seltos is built on a new-gen platform called K3 and comes with far more advanced tech. Especially when it comes to the infotainment system and connectivity. 

Because the Seltos engines are unchanged from before, we know what to expect from them - whether the 1.5 naturally aspirated petrol or the 1.5 turbo petrol. Since your driving is 60% city, we would stick with the 1.5 petrol IVT, as it is the smoother and more efficient powertrain overall. 

Kia, like Hyundai, tends to be reliable in the long run - as you've no doubt seen with your Venue - and maintenance costs are reasonable too. The Tata Sierra has promise, but its all-new engines are as yet unproven, and in our experience. While its 1.5 turbo petrol is smooth and powerful, the 1.5 naturally aspirated petrol feels underpowered in this size of car.