Difficult, yes and no.
Yes, because it is a first glance, do you trust the person with whom you might share intimity, pain or plaisure. For my self, being submissive, I need a Dominant to be overwhelming to me. Then I see a person who is well dressed and take care for itself. But there might be dominant persons who look different because of what ever reason. On the first sight I wpuld say no. But if you never try to know a persons inside you'll never know....