This is a basically a matter of style and personal preference; one is not "better" than the other, and they are equally effective in attracting attention. Two & a half--dimensional (2.5-D) flat-relief art can be bold, easily recognizeable, and highly stylized (like a logo, a symbol, and decorative designs), whereas three-dimensional (3-D) sculptured bas-relief art, is more realistic, contains more detail, and often (but not always) has more blended colors. To appreciate 3-D art, it should be viewed fairly closely (5 - 10 ft away) (e.g., a wall or podium plaque), whereas 2.5-D art and text can be viewed from further away or from a moving car and still look great. Many (but not all) of our wall plaques use 3-D art, whereas most of our outdoor and commercial signs use 2.5-D art. We make 2.5-D art by CNC multi-level flat surface routing, sometimes using 4 or 5 levels, whereas 3-D bas-relief must be made using our computer-controlled 3-D routers or occasionally by hand-carving.  Many times the art requested by a customer does not lend itself the 3-D carving. Signs or plaques with custom 3-D designs, which require new software models or hand-carving, can have prices more than  over twice that of  2.5-D designs.