These answers are specific to areas. A CMA by a Realtor will provide answers for you. A national and general comment on CNN yesterday by an economic expert indicated that "...Condos are overbuilt, therefore, there may be a bargain..." (If you mean townhome as a condo.) Appreciation was seen here for 25+ years, but the last two years have proven to be different.
Historically single family homes have had better appreciation. Right now condos are not moving quickly in this area. Significant price appreciation isn't exactly right around the corner for either type of property
I'd focus on what type of property fits your specific needs best.
Lots of different ways to look at this....probably there is more room for negotiation on an existing(old) home...but the home builders may want to be more negotiable now too..there may be a "spec" home that they built that they may want off their inventory....On resale value...personally, I think single family homes may be just a little higher than townhomes(more families....townhomes have stairs...so you may not have as many seniors looking at them)..but with all the changes we have with lifestyles...divorces, singles and so on there are lots of buyers for all properties