That's a big question, and perhaps one hard to answer definitively. Much depends, of course, on the state of the market, and the condition of the property. Plus, condos and townhouses are two totally different types of housing, and are difficult to compare. That said, which one makes the best investment depends on what you’re using it for, our experts say.

In Manhattan, the median sale price of a townhouse has increased 33% over the last decade, to $3.59 million from $2.7 million, according to data from appraisal firm Miller Samuel. Meanwhile, condo median prices have gone up 55.4%, to $1.25 million from about $804,000, the data show. (The company has loads of data on historical price trends, number of sales and more, if you want to dig in.)

Townhouses make up a comparatively small portion of the housing available in New York City, and tend to offer more privacy and space, as well as the freedom from rules governing renovations, subleases, and the like. And while you won’t pay monthly common charges, you’ll be responsible for repairs and other upkeep.

Meanwhile, in a condo building, you probably won’t be on street-level, which is in general safer and quieter; you may have access to amenities like a gym or roofdeck; and a property manager will probably handle much of the maintenance and cleaning of common areas. But, of course, you’ll be living close to your neighbors -- with all the potential for noise, smells and other annoyances that implies -- and you’ll pay fees to the building every month.

From the perspective of an investment, here are a few points to consider:

If you plan to rent it out:

“If either is being considered as a true investment -- you won't live there but instead rent it -- it can depend on future supply and demand balance for particular sized units,” says Donald Brennan of Brennan Realty Services, who sells both condos and townhouses.

In New York City, the rule of thumb is that, even on a per-square-foot basis, larger spaces fetch more than smaller ones. So if you had two nearly identical apartments -- one that’s 1,000 square feet and another that’s 1,200 square feet -- the bigger one would sell or rent for more than 20% above the smaller one.

Additionally, the bulk of renters in the city are looking for smaller apartments, notes Brennan. “This would indicate that on a per-square-foot basis you are better off buying a small condo and renting it instead of buying a large townhouse and renting it,” Brennan says.

If you plan to sell it for a profit:

This is typically what people mean when they want to buy a property as an "investment," but in this case, it gets tricky because the population of purchasers interested in each housing type doesn't fit the same profile. “It is tough to compare the two property types because they generally represent two different types of buyers,” says appraisal expert Jonathan Miller, president of Miller Samuel.

“When most people compare the two housing types,” adds Miller, “they use the argument that townhouses generally cost less on a price-per-square-foot basis than condos, inferring a buyer gets more for their money and therefore is a better investment.”

But don’t be fooled. First, average condo prices are inflated by sales in expensive new developments, whereas townhouses generally aren’t (because not a ton of developers are building new townhouses and skewing the data), Miller notes.

Second, townhouses are measured from the outside of the walls, while condos are measured from the inside of the walls, he says. If they were measured the same way, townhouses would be roughly 15% smaller, which would drive up the price per square foot. 

And lastly, even condos that are the size of a townhouse may sell for more money if they’re on a higher floor: the view alone is like an amenity that can increase the price.

Keep these factors in mind when you’re looking at places to buy.

If you plan to live there:

The bottom line if you plan to use this place as a home? Don’t pick it solely on investment-related criteria. "Make the decision based on what type of home works best for your lifestyle," Miller says.

And Brennan would agree: “I'm from the camp that thinks your home shouldn't be viewed as an investment, assuming you live there. All's fine and well if the asset appreciates in value, but the greatest value received should be from utility.”

Leigh Kamping-Carder is a senior editor at BrickUnderground.com, the online survival guide to finding a NYC apartment and living happily ever after. To see more expert answers or to ask a real estate question, click here.