I would recommend fiber-cement trim. Fiber cement is a sustainable material; it is moisture, rot, and insect resistant, nearly maintenance free, and can last more than 50 years.
HardieTrim fiber-cement boards are suitable for a wide range of uses, including window trim, gables, column covers, friezes, and fascia. The product is covered by a 15-year transferable, limited warranty. Colors are factory applied and fade-resistant, so you can avoid the expense of painting, though boards may need some touch-up after installation.
Other fiber-cement manufacturers include CertainTeed and Nichiha.
Fiber cement does cost more than vinyl trim, but it will outlast any vinyl product. Qualified installers should be hired to perform the work, and installation costs may be high compared to some materials. Because of its sturdy composition, fiber cement can "eat up" saw blades?but that, to me, is proof of its durability.
For More Information
Read Connie McCullah's Ask A Pro article Which is greener: fiber-cement or vinyl siding? to learn more about fiber-cement products.