Detached homes are generally easier to sell. Some buyers will dismiss attached homes because of the potential for "noise" issues, etc. and for re-sale you want to buy a property with the widest appeal. Having said this, other factors come into play... such as location of these homes, quality of materials, etc. A local buyer's agent can best advise you.
Associate Broker, Massachusetts, New York and Connecticut
Berkshire Property Agents
12 Railroad Street
Great Barrington, Massachusetts 01230
Things may be different in your market than mine, so lean on the local answers more heavily, but detached homes seem more desirable to me. I suspect they will appreciate better when the market comes back and have a larger potential buyer's pool than attached housing.
What does your local agent think? I hope you have a great local agent representing you and not the builders/sellers agent.