The obvious answer is....that is all depends on the salesperson. We are a commercial integrator and my #1 goal is to build long lasting relationships with my customers. Relationships are built on trust. To build trust the customer must feel like you are looking out for their best interest at all times and you must be knowledgeable, reliable, and competent. Plus a little bit of personality goes a long way too. So, to close a new deal it does take someone who can effectively communicate value, differentiation, and disseminate a sense of integrity (you need to come off as being trustworthy). Having an outstanding reputation in the local market helps with this significantly. In addition one of the main abilities I look for in a potential "solutions engineer" candidate is someone who can take a complex set of ideas and communicate them effectively to a laymen.
With that said, I always found a team approach as being one of the more effective ways to close a deal, whether with a new or existing customer. The team being....
1. The customer's internal support staff (IT, security, facilities)
2. The integrator
3. The manufacturer
4. The consultant
Each brings its own value needed to plan and execute a project successfully.
The consultant is expected to have an unbiased broad sense of life safety and security technology knowledge, however, once we earn the customer's trust it often makes the consultant unneeded (unless required by policy).
As the integrator just like the consultant we are expected to possess a broad sense of life safety and security technology knowledge and best practices, in addition we typically possess the most up-to-date and practical real world experience, and are the boots on the ground to get the work done, thus assuming the most risk in delivering the project.
In my mind the manufacturer is expected to have the most in-depth knowledge of their product, and the customer's support staff is expected to have the most knowledge of their environment.
Therefore, I see the (4) roles as critical and when they work together as a cooperative team, most of the time you will have a successful project however like the consultant potentially not being needed if a customer has a trusted integrator that can design and execute a project, the integrator may not be needed if the customer's internal team can work directly with the manufacturer to design and implement a project.
However, not many manufacturers have all the resources to implement a turn key project for the customer, not all customers have the internal resources to work directly with the manufacturers to implement a turnkey project, and not all integrators have the high level of trust with their customers for them to not feel like they need a consultant.