My black and white comics obviously require lined art.
For color comics, I rather strongly prefer lined art. It's the industry standard for a reason, even it it's more expensive, often requiring a whole 'nother artist to do the inking and yet another to do the colors, especially for a traditional print comic. However, it's not all cut and dried. The key is to know when bold, thick lines are appropriate, and when it's necessary to do a thinner or even borderline nonexistent line. Lineless art can look all right to me if the colors are crisp and shapes are clear, however, especially with my eyesight reflecting my age and health, it's generally harder to see and make out the shapes.
I also feel it's worth pointing out that the best "lineless" art still technically has some lines, although artists doing that tend to be clever, making the lines thin and making them whatever color they need to make them look less conspicuous.