1) Real estate price = land price + house price. The house price goes down when it gets older. But land price usually goes up. Town homes have less land than a single house. Its value goes up slower than a single house at same location. You can always to rebuild your single home, but for town home this option may not exist.
2) At most time your neighbor is quite. Town home is good as single one.You wouldn't hear day to day regular noise. If they like loud music, you will hear it even both of you close all the windows.
I will consider a good location town home. The price deference between a town homes to a single is so big at such location. It makes a town home more attractive. If you buy a new development, their price deference is much less. Try to get a single if it is possible.