EIN without LLC
I suppose the advantage of having an EIN as a sole proprietor (without filing an LLC) would be that you would save on the registration and - in many states - maintenance fees of having the LLC.
However, by having an LLC you would enjoy the benefit of limiting the liability of the business only to business owned assets. This effectively separates your personal property from the business, which if god forbid your business was ever sued, may protect your personal finances.
It would definitely be a good idea to consult your business plan with a licensed attorney to understand the various implications of having registered legal entity vs. just using an EIN as a sole proprietor.