brokeenthusiast

I live in India and I'm looking for a used Merc. My dad says he wants a newer Merc because it'd be easier for the laws and everything if it's newer. The cars in question are the w124 e220 manual transmission and the w203 c200 cdi '02 and '03(and yes, i do know its a diesel fyi).So i'd be comparing problems. I'm not looking for prestige on a budget, but a good car on a budget. So, I have two questions: one: which would be better interms of maintenance and ease of ownership(on the pocket,comparatively because as far as cars go, the tech stuff doesn't matter much to me)? And second: I'm looking to get a natural gas kit, but since it's an obd1, is it possible to get sequential natural gas kits for obd1's?
Thanks a million
P.S: I know this is apples and oranges, but i need to know which one gives me less of a pain in the neck