There are positives to both of these options. Both provide customers with the ability to view, shop, and interact with your online web presence, whether it is a blog, like E-Commerce Gorilla, an E-Commerce storefront, or an online community forum.
So what are the main differences from an upkeep and optimization perspective?
Individual Mobile Website or Theme
Ability to generate device-specific interfaces
Ensure customers can navigate and interact in the most seamless way possible. We know people hate typing on mobile phones so perhaps your mobile theme would act more as a personal shopper based on a series of simple questions addressed to the visitor.
Content can be optimized to increase conversions based on device trends
If people are using the device more for research than purchases, prior to purchasing from a desktop you can increase the presence of reviews and testimonials.
Increased expense in platform development and maintenance
Every platform is unique. To accurately target all major mobile devices would take a sizable budget/time commitment.
Increased time in analytical review
In essence, utilizing a mobile-specific website or theme is creating another website. Even if you are dynamically adding content from a CMS, each web presence should be monitored and treated as a separate entity when it comes to monitoring social interactions.
Single development and maintenance costs
While it is a newer concept for many entering into the web field, it provides the ability to focus budget on global improvements versus having to optimize on a platform by platform basis.
Automatically adjusts to new and emerging form factors
Limited device-specific customization
With the ability to cater to such a wide variety of device form factors comes the need to make generalizations. Yes, you can limit types of information seen and the placement on devices. Depending on dimensions, these are still done through estimations and content placement.
Inability to target specific device interactions
So this is a little bit of a misnomer. Yes, you could target specific devices, but at this point we are talking about a hybrid between a responsive and mobile website. Again, you are now beginning to make modifications on a device-by-device basis. So for this discussion, the answer is that you can only target based on screen dimensions.
Bringing it together
So which direction is best for you? Without trying to take the copout route of saying it depends on your needs, it really does. However, I will make some generalizations that will allow you to more adequately discuss your options with your web developer.
What is your overall web budget? Can you afford to have maintenance on multiple platforms? If you are a smaller business, the answer is generally no. If you are a small e-commerce website, this can go even further in the no category because individuals making purchases on a purely online entity will generally do so from a desktop platform. Yes, this is a generalization and yes, this trend is changing. However, for the moment it holds true.
Are you a brick-and-mortar store with an online presence? If so, do you need customers to interact with your brand in a local market, such as with store locators? If yes, then perhaps a mobile website/theme is right for you. It really comes down to your customers needs. How do they need to interact with your brand or website to maximize its value?