there's a wealth of knowledge if you do some searching around:
Which is Better - Manual vs Automatic Transmissions?
that is reasonably basic enough for you to get a good understanding on the differences.
As pointed out earlier, what sort of engine capacity are you looking for? that will further determine if auto/manual suits your condition.
An automatic transmission has more working parts, although not too much but still there is a portion of power lost in the driveline as auto requires more working compared to manual.
If you're looking at an engine capacity of under 1.8L you're better off with manual, any higher I'd go for auto - but again it depends what car it is, how many gears available for that auto and what are the servicing costs.
Cities like Islamabad = auto would be fine, road conditions allow the auto transmission to function properly, compared to the rougher roads where it would be a nightmare for the auto working out exactly what gear to be in at the particular time....