Take a position: Product functionality is the key to brand success versus product design is the key to brand success.
The “form versus function” debate applies in many arenas, including marketing. Some marketers believe that product performance is the end all and be all. Other marketers maintain that the looks, feel, and other design elements of products are what really make the difference.
Of course, the best products will have both form and function. However, if I had to pick one that is more important, I would argue that it is function.
There are many products for which the function is much more important than what the product looks like. For example, Toyota's Prius is not a notably good looking car. But people like the fact that it gets good gas mileage and that it makes a statement about being "green." As another example, iPhones are not all that good looking. But people like the variety of functions that they can perform so they do not worry about having to hold this rectangular thing up to their face while they talk.
Whether a product's function or its appearance is the selling factor has been a long standing debate. Ultimately, in the longer run, a successful product has to have both a good appearance and remarkable performance (think of the Toyota Corolla and Honda Civic). Personally, I would pick functionality and performance over the looks/design of a product. Consider that Sony and Samsung make better designed smartphones and a whole range of them too—however, it is Apple's iPhone that sells much better, even though one has to learn a different operating system and the "Apple" way of doing things (different connector, etc.). The iPhone consistently beats Samsung and Sony in sales. Similarly, Dell and HP manage to sell many more laptops than Apple, because you can get the same features for a much lower price than Apple (which is kind of the opposite of the smartphone market). The products from Dell/HP are average-looking, while Apple makes "good-looking" (in Steve Jobs' own terms) Macs.
There are a number of factors other than performance and design, like brand loyalty and value, that need to be considered as well when formulating your sales and marketing strategy.