When you buy the car since its a old car and chances are people dont maintain it well you will have to visit workshops initially to get everything sorted, stuff like suspension components, fluids and any other issues. after you have sorted it then its very very reliable. i in my one year of ownership have not once gone to any workshop because any part broke or malfunctioned. only to fix parts to brand new specification. if you get a good one that initial period and cost will be reduced but you should still keep in mind 2-4 lac budget to restore it perfect factory spec given the condition of cars on the market.
now once its restored it will be way more reliable than any japanese or local car. take for example oil change intervals in local cars you have to change oil after every 5k in this you have to change very 8k or if you use Original MB or fleece filters then after 15k km.sparkplug intervals are 50k km plus, there is no concept of tuning or throttle body cleaning. stuff like engine mounts are about same cost as corolla. brake pads too are similar cost to brand new parts of corolla though some components can be expensive as well.
as far as parts availability goes every single nut and bolt and washer along with large items like bonnnet, differentials or engine components can be bought Brand new right from factory through shahnawaz instead of kaabli or junkyard parts in case of japanese cars. used parts option is also available though i wont recommend it and some simple parts can also be imported form dubai using INH etc though they are not a substitute for original parts form shahnawaz. so no issue at all for parts. but shahanwaz doesnt mean you have a blind eye, you must take personal interest in the repair and not just leave the car alone with them to sort out as they can too mess it up sometimes. they are also reluctant to entertain grey import cars who already have major faults before to keep this in mind. only 6 w203s in lahore are currently being maintained by them including mine no one else goes to them, they mostly handle newer cars majority are w212 e class and s400 hybrids and some w204s and one odd 4x4s and sports cars of mercedes.
leg space in the rear is good compared to 10th corolla but less than 11th gen corolla. also only two people can sit comfortable in back for long journeys as there is a very big hump in the centre for the driveshaft which makes sitting in cetre awkward. although the centre passenger does have a proper headrest and three point seat belt instead of just a lap belt. for the two passgners its much more comfortable than corolla as seats are designed better and more supportive they are also laid back and have independent AC blower control as well as AC vents in the feet and sperate lightning controls, better designed armrests, door opens way wider so easy to get in out though its quite low so not good if you have back ache for example to get in out of car. i have picutres in my thread regarding rear seat space you can judge for your self. but for three passengers 11th corolla is bigger and does have more legroom though it may not be as comfortable. trunk space of w203 is way bigger than corolla and rear seats can be folded completely flat so you can carry very large items. rear passengers also have their own curtain airbags.
what i meant regarding the suspension was its more expensive to fix and more delicate in the sense that it has fully independent suspension all round like honda and compared to corolla which has two control arms made of heavy solid metal this has 4 control arms made up of lightweight alumimium and with lower profile tyres the ball joints and bushings wear out more easily especially since few people would have replaced them on time. the cost of both upper and lower control arm of only one side is 42k, front shocks are 70k, zlinks 10k etc so if these things have not been serviced it will be expensive, one you have replaced them the car will drive so well youll forget everything else and you can expcect at least 70-80k km of good life from them in our conditions provided they are replaced properly for example tightening the bushes with the vehicle on the ground and wheels loaded not in the air. so compared to corolla the suspension is definitely going wear sooner especially on rural roads with chances that it has already worn so will have to factor in this cost.
regarding the ground clearance its lower than civic, mine doesnt have large wheels and is on 60 profile tyres so its a bit lower than usual with 4 people i have tried it can hit speakbreakers in lahore 30-35% of the time. but if you go across never had a issue. i never found the ground clearance in the city a hinderance.
btw all these points i have better illustrated in my thread, try to read it many of your questions will be answered i think, feel free to ask for anything else.