I wholeheartedly agree. This is a long term commitment that you are getting into, as for the differences and points of strengths between the two breeds, they are both two very different breeds, you can read up quite a bit on both on the internet. But when it comes down to it, your best bet is to find a good breeder or a person experienced with one or the other breed, and really talk to them, spend some time with their dogs, and really find what breed best suits your lifestyle.
Dobies are active dogs that want to be with their person. They thrive on having a job in their life. Unsocialized, unworked, untrained, they can be a liablility to own. If you have a busy lifestyle, they may not fit for you. There are many health issues that can plague the breed, so it's very important to look for a good breeder that is knowledgeable about this, and health tests their dogs. That probably isn't going to be the "cheaper" costing dog you find, regardless of the breed. If you skimp on the health testing to get a less expensive dog, you may find yourself really paying out later in both money and heartache down the road.