Absolutely, it's alright. Developed intuition through experience is often better than a detailed decision matrix in terms of results. When experts rely on their intuition, it's usually called "experience" or "expertise".

It might be worth reading 'sources of power' (a book about decision-making and experts) to cull some useful stats that you can use to back up your approach to making decisions:
http://www.goodreads.com/book/show/65229.Sources_of_Power

Of course, the key element to all of this is to be able to establish a track record that you can demonstrate. Telling someone to "trust you" works well if you've got a demonstrable track record of past successful projects. If you can't show that to a new customer, it'd be harder to sell.