Adjusting multiples of comparable companies

I realize that many people are in favour of using the market approach to valuing a business and adjusting the multiples of publicly traded companies to take into account different size of the companies, growth prospects, profit margins etc. I must admit I have an inherent problem with such an approach. For example, if by adjusting the multiples you get from EV/EBITDA = 6,7 to EV/EBITDA = 6,4, you haven't really done much. If, on the other hand, you get from EV/EBITDA  6,7 to EV/EBITDA = 4,0 - is this really still the market value? Because let's be honest, adjustments reflect your views (or some other analyst's views) and the model that you use for adjustments. And such models don't have much empirical backing.

This is why I'm in favour of using multiples of publicly traded companies to value shares in private businesses only as a sanity-check (i.e. control) method, to see to it that your DCF valuation (as a primary method) isn't way out of any realms of reality.