Hey there,
I would just like to add my 2 cents regarding Liana as I have been using one since the last 10 years.
Firstly, Liana is definitely more powerful than city simply because it's engine has Dual Over-Head Camshafts(DOHC) as compared to City's Single Over-Head Camshaft(SOHC). Now, this does give you more power but at the expense of fuel economy. So City will give you a better fuel economy than Liana. Moreover, City has 2 sparkplugs per cylinder which is also why it has a better combustion efficiency and fuel economy. This does mean that every time you change the sparkplugs, the cost will be double that of Liana.
Secondly, Liana has more height as compared to city and length and width of both cars are same. I know because I have with me old brochures. You can try it yourself, you will find cabin of Liana to be more airy than City.
Thirdly, in terms of handling and comfort. Liana's suspension has front and rear independent suspension. McPherson strut in the front and multi-link in the back, City's rear suspension is semi-independent because it uses a torsion beam bar. So both its rear wheels share a torsion beam which is mostly fixed and has very limited flexibility. And Liana's suspension are softer than City's and coupled with 4-wheel independent setup, its absolutely absorbs the shock over bumps and potholes.
Now, I know it seem that I am telling all pros of Liana which I am. You see, Liana is a car for people who want to bear the burden of maintenance and fuel in order to get maximum driving pleasure, comfort, performance and features. Liana excels at everything when compared to City. It has ABS brakes, immobilizer to prevent theft, central locking and keyless entry(LXi only) as well as bigger stock wheels and split folding rear seats.
However, you do also need to consider practicality in terms of maintenance and fuel economy etc. Hands down City will absolutely give you better fuel economy and I have personally found the quality and design of its parts to be better and more reliable than of Liana's. And if you observe the touch and feel of City's controls, you will find that they are more refined than Liana's. When you operate the outer door handles, they are softer and closing closing the door also feels more reassuring. The seating position of city is better than Liana because it relatively closer to the ground and the seats themselves are shaped to provide better comfort and a snug fit. Liana's seats are rather flat and positioning is quite high.(Sometimes feel like I am inside a Hilux lol.)
So in the end, the decision is totally yours, what you feel is right according to your needs, wants and preferences. This information is here so that you are able to make an informed decision.