We face competition at every stage of our lives, and the way we want to handle it becomes the deciding factor and makes us stand out of the crowd. It becomes most difficult when are judged on same grounds. During bidding, an effective proposal is the deciding factor to win.
In a typical scenario,
labour categories to bid
number of hours
clients and their specific requirements,
are the factors which are common
A few things that could differentiate you from others are,
Qualification
Experience
Price
Competition management
Process of execution
And most importantly your proposal presentation skills which leads to winning the bid. It is also important to inform the client about the course of action taken for you to deliver results.
This is when effective proposal writing becomes a competitive advantage.

Tip: More focus on the result deliverables than simply following the instructions in RFP. Also explaining why the results matter would make it more impressive.

Let’s consider two proposals and compare them for better understanding of the importance of an effective proposal.

Proposal B definitely has an edge to it and will likely be picked even though
the client expects the same of both,
both must offer the same,
and the benefits mentioned in proposal B is also delivered by A
as it sounds much more impressive, effective and considerate when compared to A. [Proposal B is written from the client’s perspective]
This difference is sufficient to change their scores and win a higher price during the bid!