Dear Mr. Nair,
According to your monthly running, I would suggest you to go for Ciaz Zx AT. Its a good car and at the price point on which it is being offered at present it is VFM
buy. The features are good, overall appeal is nice and would be a niggle free experience.
The reason I exclude all others are:
a) Honda City: Build Quality and the N.V.H levels are slightly on higher side. Comparatively feature wise also, Ciaz is more loaded than Honda City 2014.
b) Xylo: I personally don't find it that attractive as family car. Though it is one of the most practical 7 seater vehicle by Mahindra. At present it has been recalled for some technical issue. I would suggest you to have a look on Ertiga Zxi too.
c) Scorpio: I wouldn't suggest the diesel one at all. Plus as you are 4 people most of the time then such big vehicle is not required to be honest. It too has been recalled by Mahindra.
Maruti's after sales has an edge over all the others so this way as well Maruti shall be a good buy.