The choice has more to depend on one's likes, dislikes and choices.
Row houses are usually not high rises and have o vertical rises, with more than two floors. So an average flat will generally have minimum two portions or more touching in common with another flat. They are the ceiling/foor, side walls etc. Some people do not like having more common portions. So many flat builders advertise as minimum common walls or nil common walls. Such constructions will be more costly as they have to use more space.
But row houses can have mostly maximum two sides common, but that can still give a feel of 'enclosed' or 'sandwiched'. But given all other parameters like same area, cost, locality etc being almost same, I would personally prefer a row house. This is because; in flats there is always a possibility of toilets/bathroom leaking. Similarly the utilities like drains etc depend upon the use style of other flat residents and we have to bear the brunt of it one way or other ( Of course nowadays the residents are aware and know about community living and inter-dependence)
In flats as the ground is shared by all the vertical growth, the 'per flat undivided land share' is very minimal in comparison with a row house of similar usable area. In some row house constructions, sometimes the house owner has the ownership of land also. In that case it is definitely more preferable than a flat, as the land value goes rising at a fast pace.
Unlike ina row house or flat, living in an independent house has the one plus point-that is we are independent. But in that case we have to face single handed everything and find solutions. In flats or (even in certain row house community living) there are other residents who are all, jointly managing the affairs.
Whether you buy a flat or row house in resale, you have to ensure that the documents of title for the seller are without any problem. The construction has got all statutory permissions, and there is no due to any government bodies, the land title is clear and unencumbered. You have to make sure that there are no cracks and leaks and the seller has not 'hidden' any seepage marks etc. Then you have to ensure about water and drainage facilities.
If the row house has independent ownership of land, if the walls of each house are practically separable for needs of any maintenance or reconstruction, if there is permission and freedom to do re-constructions, the buying a ro house is far better than buying a flat. If the row house is inside a gated colony, then there is no concern of privacy and security also.