Yellow letters vs. MLS

[Michael Norris]

I have been analyzing a number of properties on Zillow using the Bigger Pockets rental calculator and I am finding, from a price perspective, that most houses in my area just aren't a good fit for rental properties.  The ~20% that are  good introductory prices for rentals  are in need of a good rehab. This is fine, I have nothing against a rehab, but what I am questioning is:

• What would be the best tool to generate the lowest price on a property,  a marketing campaign (yellow letter/ postcards) or a real estate agent? 

Being a new investor, I want to say that the lowest average possible price that could be negotiated from a lead off of a marketing campaign will be better than the lowest average possible price that could be negotiated on a property off the MLS. I come to this conclusion, that the marketing campaign will be better, due to working with motivated sellers (more liable to negotiate). I also know that in order to get the best price possible, the wholesalers are running their own marketing campaigns. Also, the cherry on top would be avoiding the ~3%, the costs of doing business with a real estate agent.  

I understand that real estate agents preform a lot of tasks ex. provide tours of properties, discover properties that fit the clients needs etc. All of these tasks help to validate their cut of ~3%. While looking at things only from a price perspective, are rental property investors stupid/ lazy when purchasing deals straight from zillow/ trulia/ MLS? --- gee, now I know why investors are motivated to get their real estate license. haha