I'm not sure size of business is the main distinction, although it might have some bearing. What I think is the most important distinction is artistry or advocacy. When I practiced litigation, I turned down a few clients because I didn't think they had a legitimate case. But most of the time, I was too afraid of my own liability to tell them they didn't have a legitimate case, so I would quote them a very high retainer or otherwise convince them I wasn't the best lawyer for them. Later, when my practice changed, I told clients I didn't handle litigated matters, so if the case went to court they would have to change lawyers. If they needed a lawyer who was willing to litigate, I offered to act as a consultant, helping them interview litigators to find the right one for them (at my regular hourly rate).
But as a consultant I often told clients that there were a few lawyers who were like OJ's dream team. They were good actors. They could take any case and make it convincing. However, most lawyers were not that good, and if they didn't believe in their client's case, the judge or jury would be able to tell, even though the lawyer did his or her best and never failed in any duty of care. Effectively advocating something you don't believe in is hard for most people, and rightly so. Integrity is an important value and a good character trait.
Could I represent a heinous criminal? If I were an experienced criminal attorney, of course I could. Could I make my words convincing to a judge or jury if I disbelieved my client? Probably not.
The same applies to art. The artist's feelings about the event are communicated in the artwork. If you are painting or photographing something that you think is ugly, but are required to make it appear beautiful, how well will you succeed? Some artists are better at that than others. I looked at the
photographer's website and came away with the impression this photographer sees herself as an artist who puts a lot of herself into her work, and would simply not be able to make a gay wedding look as beautiful as she can make a traditional wedding look. What if she were honest about this with the couple? What would you say in that case?