I have had xli (2003), City (2004) and Lancer (2006) so let me give my experience ...
1.Body - I HATE xli.. soo sick of it. Both City and Lancer have nice shape. Lancer has MUCH better stock equipment, 4 speakers (compared to 2 of city), Yokohama tyers, solid body, japanese asssembled.
2.Engine - They are both good. City has slightly better mileage than lancer.
3.Interior - Love Lancer's interior but city isn't bad either. City's deck looks better than Lancer's but lancer's quality is better Forget xli, the thing is more expensive than city and lancer and doesn't even have power windows!
4.Spare parts - both are available, both have 3S. If you buy a city's air filter from 3S it costs 1300.. exactly same as lancer. If you go for local parts, they'll be cheap for both the cars.
5.New Model release: not sure about xli or city, lancer's new model will come next year probably and it's HOT!
6.Consumption - City is better than Lancer. Xli is probably same as Lancer don't exactly remember.
7.Best Financing Bank - not sure about this one.
8.Best Dealer in Town(Isloo)with the shortest ETA - Lancer is selling like hot cake these days so i gues there is a wait period of 1 month of hot colors. Not sure about City.. XLI is overpriced, and overhyped.
Lastly, I am not sure about resale, XLI sells like hot cake City I had to sell thru a dealer. Lancer i am trying to sell and had an offer of 745k ... so let's see.