Generally speaking, we don't like rooftop cell site marketing agreements. If your property/building is unique- the carriers will come if they need it and no amount of marketing by either company will get them to come faster or make them use the building if they don't already need it. If the property is not unique, then there may be some benefit to having it marketed to help it "stand out" from the other nearby similar buildings. If you do enter into a rooftop marketing agreement with either company, it is important to limit the "exclusive marketing period". No reason to enter into a long term lease with either Blue Sky Tower or Crown Castle so that they can tie up your property and wait to see if someone approaches you. Furthermore, we typically recommend two different percentages- a higher percentage to the landowner if the carrier walks in your door and talks to you as opposed to Blue Sky Tower or Crown Castle bringing them to you.
In regards to choosing between the two (or the others that do site marketing), I don't believe that either Blue Sky Tower or Crown Castle will be marketly better at negotiating a greater total dollar amount. I believe that Crown Castle would be generally more likely to get prospective tenants interested just on the basis of their nationwide agreements and substantially larger sales force, however, Blue Sky may have better connections in the Northeast. 20% is a significant difference though and I would be hard pressed to pass it up.
If you need some help reviewing/discussing the business terms of the agreements, we can help. If you need an attorney to review either agreement- we would recommend Cell Tower Attorney