Swirls may be better for catching the eye and getting a second look/click than actually securing a sale. The feathered mantra swirl seems to attract attention.
I've never had any complaints about a color or swirl, but people do seem to like the marble look of ITP swirls, the rings of (faux-) funnel swirls, etc. But my plain uncolored soap sells just as well.
I've noticed that my friends ooh and aah over the appearance, then gravitate toward scent. My focus is on quality. Generally my recipe is 15% co, moderate sf, with the intent to balance bubble factor and protecting natural skin oils - and plumbing! My friends don't mention that (but hopefully that's because with my recipe, with sodium citrate, they don't get a chance to notice possible problems!
I should just quite worrying about what they like, and make the best quality bar I can. I know one teenage guy who comes to me asking to buy my soap. He has acne, and his Dr. gave him a list of ingredients to avoid and asked if my soap had any. Bless his heart; he's a hard working college student who hopes to design robotic prosthetics in the future. I give him my personal supply of plain jane "winter" soaps, (grass fed tallow, unrefined avocado, and only 5% co) because the acne meds dry his skin so much. He feels guilt about the free soap, but I tell him my payment is the satisfaction of knowing my hobby is benefitting someone.
Thanks again for everyone's suggestions.