In general condos are a little tougher to sell, but I've seen some pretty bad townhouses that will take a long time to sell as well.
Key factors in a condo selling will be how much customization and upgrading has been done in the unit--if it's unique compared to the neighbors (in a good way!) it will sell more quickly. Great views on a high floor is always a winner; proximity to things like Piedmont Park always increase interest as well. If it's a smaller complex, you probably won't have as much competition when you decide to sell; some of the larger complexes in town will ALWAYS have 15-25 listings competing at any one time.
And even though these properties don't appreciate as much as single family homes, you're buying a lifestyle-- you can lock the door when you leave and not have to rake leaves or paint the house when you get home! You'll also get the tax benefits of being a homeowner, which has huge financial value.
For the young working professional the High rise is more attractive. Townhomes are more attractive to the empty nester.
Both properties can be a tough sell in the Atlanta market because of the abundance of inventory for both property types. New properties can easily be found for the same price as most resale units. It's important to list your property at the right price the first time and be able to market unique incentives to make your property stand out from the others.
Check the history of the appreciation rates, year over year for the last 5 years for both. History is no guarantee of future movement, but it can serve as a guiding light.
With townhomes, there is a bit more customization in them.
It all comes down to the market though, and right now condos are sitting and they are taking the biggest hit.
There is a huge inventory of Condos in Atlanta but you have to look at when you will sell and do you have to sell. Mortgages soon will be hard to come by with no money down so the rental market will become attractive. This is a good time to buy and hold. so you may be ain a postion to edge your bets and buy one of each, live in one and rent the other, when it comes time to sell, sel the one that is hotter on the market.
Location would be a factor, however you are within blocks of each other.
Condo are a tougher sell. Ultimately you will make the final decision. So imagine that in three years you are the buyer. which would you choose.