as the owner of both a altis and w203 mercedes i think you should go for merc if you want a second luxurious car of german lineage and therefore the luxury and prestige that follows with it, but as a daily driver it is cheaper and makes more sense to own a civic. if you get one with full service history and all maintinence being performed, stuff like suspension ATF fuel filter/pump etc not just oil changed and spark plug then the car will be extremely reliable and thee car are built to last. if you go for one which has no proper maintinece performed and original and new parts haven't been used then you will be regretting your decision.
there are no elephant expenses involved but dont compared to cars which have no service backup here such as JDM.
a oil change cost 10,000rs ATF change is 35k fuel filter an pump 70k etc. similarly new suspension components such as shocks are 60k controls arms 50k etc. so if you are not prepared to pay these type of expenses god forbid if something goes wrong or need replacing then it isn't the car for you. junkyard parts aren't good option.
that said you live in lahore so there is shahnawaz and INH both good in taking care and having all the parts you need for the car.
and its way superior than civic in features, performance and luxury.
but as a day to day car civic is excellent with minimal fuss especially if you yourself dont take interest in the car and leave it at the workshop for the work to be done without your presence.
for more info on the mercedes you can visit my thread where i have a older w203 same model range but prefacelift and alhumdulillah very satisfied with it and nor has it broken the bank despite being even older.
this thread also gives rundown of maintenance costs as well as suggestions and views of our resident Guru Xulfiqar on owning and taking care of the said car.
you can also see the various threads of new civic owners here at pakwheels.
seeing both threads and the cars in person and then making up your mind yourself would leave you with a more clearer decision then just listening and basing judgement on people opinions largely without facts as they are bound to be suggestions both ways.